How long does it take the Earth to orbit the Sun?
1 of 313
How long does it take the Moon to orbit the Earth?
2 of 313
How long does it take the Earth to rotate once on its axis?
3 of 313
What is a sidereal day?
The time taken for a star to return to the same position in the sky.
4 of 313
How long is a sidereal day?
23 hours and 56 minutes.
5 of 313
Which way do stars travel across the night sky?
East to West.
6 of 313
How many degrees does the Earth have to spin in order for a star to get to the same position in the night sky?
7 of 313
In which direction do the sun and moon travel across the night sky?
East to West.
8 of 313
What is a solar day?
The time taken for the sun to appear in the same position in the sky.
9 of 313
How long is a solar day?
10 of 313
How long does it take the Earth to complete one rotation?
11 of 313
Why are sidereal and solar days different lengths? (Part 1)
The Earth is orbiting the sun as well as rotating on it's axis. This means that when the sun has rotated 360 degrees, the sun will not be directly above the Earth anymore, as the Earth has moved slightly round it's orbit.
12 of 313
Why are sidereal and solar days different lengths? (Part 2)
This means that the Earth has to rotate slightly more than 360 degrees in order for the sun to return to the same place in the sky.
13 of 313
Why do stars appear to be directly above the Earth again after a 360 degree rotation of the Earth?
They are very distant.
14 of 313
Which seems to travel fastest, the sun or the moon?
The sun seems to travel faster than the moon, the moon taking 25 hours to appear in the same position in the sky. This is because the moon orbits the Earth in the same direction as the Earth is rotating.
15 of 313
Why can we see different stars throughout the year?
As the Earth moves around the Sun, the direction we face changes slightly each day. This means we see a slightly different patch of sky each night - hence the stars are different.
16 of 313
What is an Earth year?
The time it takes the Earth to orbit the Sun once.
17 of 313
What does this mean regarding the stars we see?
On the same day each year we should be able to see the same stars in the night sky.
18 of 313
How many phases of the moon are there?
19 of 313
What are the phases of the moon?
Full Moon, Waxing Gibbous, 1st Quarter, Waxing Crescent, New Moon, Waning Crescent, Third Quarter and Waning Gibbous.
20 of 313
Does the Moon produce light?
No, it reflects the sun light.
21 of 313
Which part of the moon is lit up?
The bit that is facing the sun.
22 of 313
What are the two types of eclipses?
Lunar eclipse and Solar eclipse.
23 of 313
Explain how a lunar eclipse occurs.
When the Earth is in between the Sun and the Moon, it blocks the sunlight from getting to the Moon, so almost no light is reflected from the Moon. This means we cannot see it.
24 of 313
What is the difference between a partial lunar eclipse and a full lunar eclipse?
A partial lunar eclipse is where only part of the Moon is in the Earth's shadow, meaning some light is reflected by the moon. A full lunar eclipse is when the whole of the moon is in the Earth's shadow, so absolutely no light is reflected.
25 of 313
Which type of lunar eclipse is more common?
26 of 313
Explain how a solar eclipse occurs.
When the moon is in between the Sun and Earth, it blocks the sunlight and stops it from reaching the Earth.
27 of 313
How do the different places of Earth see a lunar eclipse?
From some places on Earth, the sunlight will be completely blocked out, making a total solar eclipse. On many places on Earth only part of the sunlight is blocked out, and in most places no sunlight it blocked out.
28 of 313
Why are eclipses not very frequent?
The Moon orbits the Earth at an angle to the Earth's orbit to the Sun, so the Sun, Moon and Earth do not line up very often.
29 of 313
Why are partial eclipses more frequent?
The Sun, Moon and Earth don't have to line up perfectly for this to happen, only a small section of each has to be in line.
30 of 313
How are the positions of stars measured?
By angles seen from Earth.
31 of 313
Which two points were picked to measure from?
1.The Pole Star and 2.The Celestial Equator.
32 of 313
What are these and why were they chosen?
The Pole Star is a star that doesn't seem to move as it is almost directly above the North Pole of the Earth. The Celestial Equator is an imaginary plane running across the night sky that extends from the Earth's equator.
33 of 313
What are the two angles that are used to measure positions in the sky?
1.Declination. 2/.Right Ascension.
34 of 313
What does Declination measure?
Declination measures the celestial latitude, measured in degrees. (How high up the star is in relation to the celestial equator.)
35 of 313
What does Right Ascension measure?
Celestial longitude, measured in degrees or time. (How far across the star is.)
36 of 313
Why is it possible to have an angle measure in time?
Because the Earth turns 360 degrees every 24 hours.
37 of 313
How does Right Ascension increase?
The further East you go, the bigger the Right Ascension.
38 of 313
What are the 'Naked Eye' Planets?
Planets that you can see without using a telescope. These are Mercury, Venus, Mars, Jupiter and Saturn.
39 of 313
In which direction do planets seem to moving in the night sky?
West to East.
40 of 313
What are fixed stars?
Distant background stars that stay in the same position in the sky year after year.
41 of 313
What is Retrograde Motion?
The process in which a planet seems to change direction and create a loop in its path.
42 of 313
To which planets can this happen to?
The outer planets - Mars, Jupiter, Saturn, Uranus and Neptune.
43 of 313
How does it happen? (Part 1)
1.From Earth, Mars seems to be moving to the left, against the fixed stars. 2.As the Earth's orbit is small than the orbit of Mars, after a few months, the Earth over takes Mars, which makes Mars look like it is travelling to the right.
44 of 313
How does it happen? (Part 2)
3.After a few more months, Earth is moving horizontally downwards in it's orbit, but Mars is still moving horizontally, making it seem like it is travelling to the left again against the fixed stars.
45 of 313
Which planet moves with Retrograde motion the most frequently?
Mars, it appears to move with retrograde motion once every two years or so.
46 of 313
Why do planets that are further out move with retrograde motion less frequently?
They are slower moving.
47 of 313
What factor affects the speed of a wave?
The density of the substance or medium it is travelling in.
48 of 313
What happens when a wave crosses a boundary between two substances?
It changes speed.
49 of 313
Give an example of these two substances.
Glass and Air.
50 of 313
What is the equation for wave speed?
Wave speed = frequency x wavelength.
51 of 313
Which part of this equation is fixed for each type of wave?
52 of 313
What does this mean regarding the wavelength?
It must also change. Eg. if speed decreases, wavelength must decrease.
53 of 313
What is refraction?
The change in speed and wavelength can cause a wave to change direction too.
54 of 313
How does refraction work?
If a wave hits a different medium at angle, part of the wave hits the boundary first and slows down. The other part of the wave carries on at the same speed as it has not yet hit the boundary. This causes the wave to change direction.
55 of 313
What happens to a wave if it hits a different medium straight on?
It continues travelling in the same direction. The wavelength has become shorter but the frequency remains the same.
56 of 313
What does a convex lens do to waves?
Focuses them to a focal point to form an image of a object.
57 of 313
What is another name for a convex lens?
A converging lens.
58 of 313
What is the normal?
The line at right angles to the boundary at the point where the ray enters or leaves.
59 of 313
What happens when a wave hits a lens?
As it travels from air to glass, the wave slows down, causing it to bend towards the 'normal'.
60 of 313
What happens when it comes out of the other side?
As the wave travels from glass to air, it speeds up, bends away from the normal.
61 of 313
What does the curvature of the lens do?
It makes all of the waves hitting the lens converge to the same focal point, where an image is formed of whatever the light is coming from.
62 of 313
Complete the sentence. Different wavelengths of light refract by...
63 of 313
What is white light made up of?
A mixture of lots of wavelengths of coloured light.
64 of 313
What happens to rays of light as they pass through a rectangular prism?
A rectangular prism has parallel boundaries, so the rays bend one way when they enter, and then back again by the same amount as they leave. The light entering the prism is parallel to the light leaving the prism so white light is produced.
65 of 313
What happens to rays of light when they pass through a triangular prism?
The boundaries are not parallel, which means the different wavelengths are refracted different amounts. When they leave the prism, a spectrum of light is formed.
66 of 313
Which colours are the spectrum made up off?
Red, Orange, Yellow, Green, Blue, Indigo and Violet.
67 of 313
Which colour is refracted the most?
68 of 313
How can you remember this?
Red is Refracted, Violet is Very refracted.
69 of 313
What is the principle axis?
The line that runs straight through the middle of the lens.
70 of 313
What is a focal point?
The focal point is where rays initially parallel to the principal axis meet.
71 of 313
How many focal points do all lenses have? Where are they?
2 - One in front of the lens and one behind it.
72 of 313
What is the focal length?
The distance between the middle of the lens and the focal point.
73 of 313
Complete the sentence. The more powerful a lens..
The more strongly it converges the rays.
74 of 313
What does this mean regarding the focal length?
As the rays are getting converged more strongly, the focal length is shorter.
75 of 313
What is the equation for working out Power?
76 of 313
What is Power measured in?
77 of 313
Work out the power of a lens with a focal length of 0.2m.
Power = 1/0.2 = 5D.
78 of 313
How do you make a more powerful lens out of the same material?
Make it with a more strongly curved surface.
79 of 313
How does light reach a lens from an object in space?
The rays are parallel to each other.
80 of 313
Give the stages on how to draw a ray diagram for a point object. (Eg. a star.) (Part 1)
Draw 3 parallel rays, one to the centre of the lens, one towards the top and one towards the bottom. Make sure you only draw the lines to the centre line of the lens. 2.Draw on the focal point.
81 of 313
Give the stages of how to draw a ray diagram for a point object. (Eg. a star.)(Part 2)
3. Extend the middle line past the focal point as this does not get refracted. 4.Extend the other two lines to meet at the focal point. 5.This is where the image will be.
82 of 313
Give the stages of how to draw a ray diagram for an extended source. (Eg. a galaxy.) (Part 1)
1.Treat two opposite edges of the extended source as point sources. 2.Carry out the same steps for both point sources. 3.The image will form in between the two focal points.
83 of 313
How many lenses are in a simple refracting telescope?
84 of 313
What type of lenses are they?
Converging lenses with different powers.
85 of 313
What are these two lenses called?
Objective lens and eye piece lens.
86 of 313
Which lens is the most powerful?
87 of 313
It magnifies the image so we can view it.
88 of 313
What does the objective lens do?
It collects the light from the object being observed and forms an image of it.
89 of 313
How are the two lenses aligned?
They have the same principal axis and their focal points are in the same place.
90 of 313
What does the objective lens do to the rays?
Converges the parallel rays to form a real image between the two lenses.
91 of 313
What does the eye piece lens do?
The eye piece lens is much more powerful than the objective lens (it is much more curved). It acts as a magnifying glass on the real image and makes a virtual image - where the light entering the eye lens appears to have come from.
92 of 313
What is the equation for working out Magnification of a telescope?
Magnification = Focal length of objective lens/Focal length of eye lens.
93 of 313
Work out the Magnification of a telescope when Fo=4.5m and Fe=0.1m.
Magnification = 4,5/0.1 = 45.
94 of 313
What do most astronomical telescopes use?
A concave mirror.
95 of 313
What is this used instead of?
The convex objective lens.
96 of 313
What is a concave mirror?
A mirror that is like a portion of a sphere. The shiny bit is on the inside edge of the curve.
97 of 313
Where is the centre of curvature?
The centre of the sphere.
98 of 313
Where is the vertex?
The centre of the mirror's surface.
99 of 313
What is the axis?
The line running from through the centre of curvature and the vertex.
100 of 313
Where is the focal point found?
Half way between the centre of curvature and the vertex.
101 of 313
What happens to the rays as they hit the mirror?
Rays that are parallel to the axis (those from a distant star), reflect and meet at the focal point.
102 of 313
How can this be used in a telescope?
By putting a lens by the concave mirror to act as an eye piece, you can form a magnified image.
103 of 313
Why are mirrors used instead of lenses?
To collect the light from distant objects you would need an incredibly large objective lens, which would not be supported when the telescope is moved around in space. Mirrors also stop any light loss from passing straight through the glass lens.
104 of 313
What is diffraction?
The spreading out of waves.
105 of 313
What happens to waves when they pass through a gap or past an object?
They diffract at the edges.
106 of 313
What does the amount of diffraction depend on?
The size of the gap relative to the wavelength of the wave.
107 of 313
Complete the sentence. The narrower the gap or the longer the wavelength...
The more the wave diffracts.
108 of 313
What is classed as a narrow gap?
A gap about the same size as the wavelength of the wave.
109 of 313
Does light have a small or large wavelength?
110 of 313
When can you notice that light has been diffracted?
When the gap is extremely small.
111 of 313
How much radiation reaches us on Earth from objects that are extremely distant?
112 of 313
What needs to be used to see distant objects and why?
You need to use a telescope with a huge object lens (or mirror) so that enough radiation can be collected to see the object.
113 of 313
What is the aperture?
The diameter or the lens.
114 of 313
Why are lens with bigger apertures better to use for studying distant objects?
The bigger the aperture, the more radiation can get into the telescope and the better the image formed.
115 of 313
Why does radiation spread out when it enters a telescope?
Because all waves diffract when they pass through a gap.
116 of 313
What does this cause the image to do?
117 of 313
What would happen if you looked at a point source like a star with an aperture that is too small?
The dot would be dimmer and would be surrounded by diffraction rings which would get dimmer the further away from the image they are.
118 of 313
How can you get round the problem?
Have an aperture that is much wider than the wavelength of radiation you want to look at. This way the radiation will pass through the aperture and into your telescope with very little diffraction, meaning you get a sharp image.
119 of 313
Other than the triangular prism, what is another way to make a spectrum of visible light?
By using a diffraction grating.
120 of 313
How does this work?
It has very narrow slits which are small enough to diffract light. When white light passes through the gaps, the different wavelengths of coloured light are all diffracted by different amounts.
121 of 313
What does this create?
A spectrum of coloured light.
122 of 313
What can astronomers use these spectra for?
Analysing the light coming from stars.
123 of 313
What is Parallax?
An apparent change in the position of an object in the night sky against a distant background. It makes closer stars move relative to distant ones over the course of a year.
124 of 313
How long does it take the Earth to get to the other side of its orbit?
125 of 313
What is the definition for the parallax angle?
Half the angle moved against distant background stars over 6 months.
126 of 313
Complete the sentence. The closer the star...
The bigger the parallax angle.
127 of 313
What is the parallax angle often measured in?
Arcseconds/seconds of arc.
128 of 313
How any arc seconds are there in a degree?
129 of 313
Why is parallax useful?
It is useful for calculating the distance to nearby stars.
130 of 313
What happens to the parallax angle as the star gets further away?
It gets smaller.
131 of 313
What is the distance to the star usually measured in?
132 of 313
How many light years is roughly equal to a parsec?
3 light years is roughly equal to a parsec.
133 of 313
How big are interstellar distances?
Usually a couple of parsecs.
134 of 313
What is the definition of a parsec?
The distance to a star with a parallax angle of 1 arcsecond.
135 of 313
What are interstellar distances?
Distances between stars.
136 of 313
What is the equation for working out the distance to a star in parsecs?
Distance = 1/angle
137 of 313
What is the abbreviation for parsecs?
138 of 313
What is the abbreviation for arcseconds?
139 of 313
Work out the distance to a star that has a parallax angle of 0.4 arcseconds.
Distance = 1/0.4 = 2.5pc.
140 of 313
What does the absolute brightness of a star depend on?
Its size and temperature.
141 of 313
Complete the sentence. The bigger and hotter a star is..
The more energy it gives out, so the brighter it is.
142 of 313
What does the apparent brightness of a star depend on?
Its luminosity and its distance from Earth.
143 of 313
Why do stars look dimmer the further away you are from them?
As you move away from a star, the energy that reaches you gets less and less.
144 of 313
What are Cepheid Variables?
Stars that pulse in brightness.
145 of 313
What determines how quickly a Cepheid Variable pulsates?
146 of 313
Complete the sentence. The greater the luminosity...
The longer the time between pulses.
147 of 313
What is a period?
The amount of time between pulses.
148 of 313
Complete the sentence. The longer the period...
The further away the star is.
149 of 313
How can astronomers work out the luminosity of a Cepheid Variable?
It is worked out from its period.
150 of 313
How can astronomers work out the distance to a Cepheid Variable?
By comparing the luminosity and the apparent brightness of the star.
151 of 313
If you look up at the night sky, how are the stars arranged?
Most of the stars are appear to be concentrated in a bright ***** across the sky.
152 of 313
What is this *****?
The Milky Way.
153 of 313
What are the stars like that are away from this *****?
There are much less of them.
154 of 313
Our Sun is one of approximately how many stars in the galaxy?
155 of 313
What type of galaxy is the Milky Way?
A spiral galaxy.
156 of 313
Why do we see it as a *****?
We are part of its disc so we see it side on.
157 of 313
Who was the debate about the structure and size of the universe between?
Shapley and Curtis.
158 of 313
What are nebulae?
Faint, fuzzy objects.
159 of 313
How did these nebulae seem different?
Some seemed spiral shaped, but others just looked like blobs.
160 of 313
What were Shapley and Curtis arguing about?
What these nebulae were and where they were.
161 of 313
What was Shapley's argument?
The Universe was just one gigantic galaxy about 100 000 parsecs across. Our Sun and Solar System were far from the centre of the galaxy. The nebulae were huge clouds of gas and dust and relatively nearby and they were part of the Milky Way.
162 of 313
What was Curtis' argument?
The Universe was made up of lots of galaxies. Our galaxy was smaller that Shapley suggested - about 10 000 pc across, with the Sun at or very near the centre, The spiral nebulae were other very distant galaxies separate from the Milky Way.
163 of 313
What was the outcome of the debate?
1.Shapley was right in saying that the Solar System is far from the centre of our galaxy, but Curtis was right that there are many galaxies in our Universe. (At least 100 000 000 000 of them.) 2.Curtis was also right about the spiral nebulae.
164 of 313
Who helped solve the Curtis-Shapley debate? How?
Hubble - with his observations of the Andromeda nebula.
165 of 313
How did he do this? (Part 1)
He used images taken by the largest telescope at the time, and found that this fuzzy blob contained many stars, some of which were Cepheid Variables.
166 of 313
How did he do this? (Part 2)
He calculated the distance to the Andromeda nebula by working out the distance to the Cepheid variables within in, using their period and luminosity.
167 of 313
How did he do this? (Part 3)
He found it was about 2.5 million light years away which is much further than any other stars in our galaxy. He studied other spiral nebulae and found a similar result.
168 of 313
What did he conclude?
All of the spiral nebula were too far away to be in our galaxy so they must all be seperate spiral nebulae themselves.
169 of 313
What units are usually used to measure intergalactic distances?
170 of 313
The distances are too huge to be measured by parsecs.
171 of 313
How many kilometres is roughly equal to a mega parsec?
3 x 10^11.
172 of 313
What is the distance to the nearest galaxy?
Just under 0.8Mpc.
173 of 313
What is red shift?
As a galaxy is moving away from us, the wavelength of the light from it changes. It shifts from blue to red.
174 of 313
How can you use red shift to work out how fast a galaxy is moving away from us?
By seeing how much the light has been red-shifted, you can work out the speed at which it is moving away from us.
175 of 313
What pattern did Hubble find?
The more distant the galaxy, the faster it moves away from us.
176 of 313
What does this suggest?
The whole universe is expanding from a single point.
177 of 313
How could this be explained?
By the initial explosion millions of years ago that started off the expansion.
178 of 313
What is this?
The Big Bang theory. It is thought that all matter and energy in the universe was compressed into a very small space, and then it exploded 14 million years ago and has been spreading out ever since.
179 of 313
Is red shift easy or hard to measure?
180 of 313
What is Hubble's law?
Speed of recession = Hubble constant x distance.
181 of 313
What are each measured in?
Either: km/s, s-1 and km. Or: km/s, km/s per Mpc and Mpc.
182 of 313
What is the value of the Hubble constant?
Roughly 2 x 10^18 or 70/km/s per Mpc.
183 of 313
Find the distance to a galaxy that has a recession of 475km/s.
Distance = speed of recession/hubble constant. 475/(2x10^18) = 2.375 x 10^20 km.
184 of 313
How can we get a better value of Hubble's constant?
By using data on Cepheid Variables from distant galaxies.
185 of 313
What is the kinetic theory?
Gases consist of very small particles which are constantly moving in completely random directions. They constantly collide with each other and with the walls of their container. The particles hardly take up any space. Most of the gas is empty space.
186 of 313
What happens if you increase the temperature of something?
You give it's particles more kinetic energy. This means they move about more quickly and they vibrate more.
187 of 313
What happens if you cool something down?
You reduce the kinetic energy of the particles.
188 of 313
What is the coldest that anything can ever get?
189 of 313
What is this temperature known as?
190 of 313
What is the kinetic energy of the particles like at absolute zero?
The particles have as little kinetic energy as it's possible to get.
191 of 313
What is another scale used for temperature?
192 of 313
If you had a temperature change of 1degree celcius, what is the temperature change in Kelvin?
193 of 313
How many kelvin is -273degrees celcius?
194 of 313
How do you convert from kelvins to degrees celcius?
195 of 313
How do you convert from degrees celcius to kelvins?
196 of 313
How many kelvins are there in 34 degrees celcius?
197 of 313
How any degrees celcius are there in -67 kelvins?
198 of 313
How are kinetic energy and temperature related?
Kinetic energy is proportional to temperature.
199 of 313
Give the statement for this.
The temperature of a gas (in kelvins) is proportional to the average kinetic energy of it's particles.
200 of 313
How are pressure and volume related?
They are inversely proportional at a constant temperature.
201 of 313
What happens when gas particles collide with each other?
They exert a force on each other as they have some mass.
202 of 313
What happens to gas particles in a container?
They collide with the container walls, exerting a force, causing an outwards pressure.
203 of 313
What would happen if you put the same amount of gas in a bigger container?
The pressure would decrease as there would be fewer collisions between the gas particles and the container walls.
204 of 313
What happens if the volume is reduced?
The pressure increases and the particles collide with the walls more often.
205 of 313
What is the equation relating pressure and volume?
Pressure x volume = constant.
206 of 313
A gas at a constant temperature in a 62ml container has a pressure of 1.5 atmospheres. Find the new pressure if the container volume is reduced to 51ml.
Pressure x volume = constant. 62 x 1.5 = 93. 93/51 = 1.8 atmospheres (1dp).
207 of 313
What is the relationship between temperature and pressure?
Pressure is proportional to absolute temperature - If you increase the temperature, you increase the pressure.
208 of 313
How does temperature affect pressure?
If you increase the temperature of a gas, you give the particles more kinectic energy. This means that the particles are moving faster, causing more collisions with the container walls. This increases the pressure.
209 of 313
What happens if you double the temperature (in k)?
You double the pressure.
210 of 313
Give the equation linking pressure and temperature at a constant volume.
Pressure/Temperature(in K) = constant.
211 of 313
A container has a volume of 30 litres. It is filled with gas at a pressure of 3 bars and a temperature of 217K. Find the new pressure if the temperature is increased to 325K.
(3/217) x 325 = 4.5bars (1dp).
212 of 313
What is the relationship between temperature and volume?
Temperature is proportional to volume at a constant pressure.
213 of 313
How does heating up a gas increase its pressure?
If you heat up a gas, you give its particles more kinetic energy. This means they are spread out more.
214 of 313
What makes up for the lack of collisions?
As the volume is increased, the particles are more spread out meaning less collisions occur. However as the particles have more kinetic energy, the collisions are harder so the pressure remains constant.
215 of 313
What is the equation linking volume and temperature?
Volume/Temperature (in K) = constant.
216 of 313
A gas at constant pressure, with a temperature of 270K has a volume of 24 litres. Find the new volume if the temperature is increased to 315K.
(24/270) x 315 = 28 litres.
217 of 313
What did scientists used to think the Sun did with its energy?
They believed that the Sun just burned its own material to produce energy.
218 of 313
Why did they realise this wasn't the case?
They realised that the Sun would have needed an impossible amount of fuel to keep it burning for so long.
219 of 313
What did Einstein discover?
That mass could be converted to energy.
220 of 313
What is fusion?
The combining of two particles.
221 of 313
What is nuclear fusion?
Two nuclei can combine to form a larger nucleus.
222 of 313
What happens in stars?
Hydrogen nuclei fuse to make helium nuclei.
223 of 313
What happens when two lighter nuclei fuse to make a heavier nucleus?
Energy is released.
224 of 313
How is nucleus fusion made possible?
The two nuclei need to be brought close together.
225 of 313
What is needed to bring two nuclei together?
High temperatures and pressures.
226 of 313
What did Einstein think regarding mass and energy?
That mass is a form of energy, so mass can be converted into other forms of energy.
227 of 313
What is Einstein's famous equation?
E = mc2.
228 of 313
What do the letter stand for in this equation?
E = energy released. m= amount of mass lost. c = speed of light in a vacuum.
229 of 313
What happens when nuclei undergo fusion?
They lose mass and energy is released.
230 of 313
What do you have to make sure in nuclear equations?
That the numbers balance on both sides.
231 of 313
What is the atom mass and proton number of a positron?
Atom mass = 0, proton number = 1.
232 of 313
What is the role of a positron?
To conserve energy.
233 of 313
Describe the stages in the production of a helium nucleus.
1.Two hydrogen nuclei fuse to form a larger hydrogen nucleus and a positron. 2.A small hydrogen nucleus and a larger hydrogen nucleus fuse together to form a helium nucleus, two hydrogen nuclei and energy.
234 of 313
What is the heaviest nucleus that can made from fusion?
235 of 313
What do all hot objects emit?
236 of 313
What is this radiation like?
It is a continuous spectrum of radiation.
237 of 313
Do hot objects emit the same amount of all radiation?
No they always emit more of one type of radiation than the others.
238 of 313
What is this type of radiation called?
The peak frequency.
239 of 313
What does the peak frequency emitted by a hot object depend on?
The object's temperature.
240 of 313
Compete the sentence. The higher the temperature...
The more energy the photons radiated will have, so the higher the peak frequency.
241 of 313
What also increases with temperature?
242 of 313
How can we tell how hot a star is by looking at it?
A red star = low frequency = a cool star. A blue star = high frequency = hot star.
243 of 313
What type of star is the sun?
A fairly cool star as it is a yellowy colour.
244 of 313
What is does an atom contain?
Electrons that move around a tiny nucleus.
245 of 313
What are the charges of nuclei and electrons?
Nucleus = Positive. Electrons = negative.
246 of 313
How are electrons arranged?
In energy levels around the nucleus.
247 of 313
When do electrons move between levels?
When they gain or lose energy.
248 of 313
What is ionisation?
When electrons gain enough energy to be removed from an atom.
249 of 313
When are absorption spectra formed? (Part 1)
At high temperatures, electrons become excited and jump to higher energy levels by absorbing radiation.
250 of 313
When are absorption spectra formed? (Part 2)
Because there are only certain energy levels that an electron can occupy, electrons absorb a particular frequency of radiation to get into a higher energy level.
251 of 313
When can you 'see' this happening? How?
If a continuous spectrum of visible light shines through a gas. The electrons in the gas atoms absorb certain frequencies of the light, making gaps in the spectrum. These gaps appear as dark lines.
252 of 313
When are emission spectra formed?
Electrons are unstable in the higher energy levels so they tend to fall from higher to lower levels, losing energy by emitting radiation of a particular frequency. This gives a series of bright lines formed by the emitted frequencies.
253 of 313
What do astronomers use line spectra to work out?
What stars are made of.
254 of 313
What are the energy levels like for different elements?
They are different.
255 of 313
What does this mean regarding line spectra?
Each element has its own line spectrum.
256 of 313
What do these line spectra correspond to?
The energies needed for electrons to get from one energy level to another.
257 of 313
What is the photosphere?
The surface of a star.
258 of 313
What does the photosphere emit?
A continuous spectrum of radiation. This radiation passes through the gases in a star's atmosphere, which produces emission and absorption lines in the spectrum.
259 of 313
How can you use a spectrum to identify a chemical?
By looking at the position of the lines in the star's spectrum, you can work out what chemical elements are present in the star's atmosphere by comparing it with a known spectrum in the lab.
260 of 313
How is a protostar formed?
Stars start off as a cloud of dust and gas - mainly hydrogen and helium. Gravity causes the denser region of the cloud to contract very slowly into clumps. When these clumps get dense enough, the cloud breaks up into protostars.
261 of 313
How is a main sequence star formed? (Part 1)
The protostar continues to collapse under gravity - reducing in volume. This makes the particles more squashed up, increasing the pressure and temperature. Eventually the temperature at the centre of the protostar reaches a few million degrees.
262 of 313
How is a main sequence star formed? (Part 2)
The hydrogen nuclei start to fuse together to form helium. This releases an enormous amount of energy and creates an outward pressure to stop the gravitational collapse.
263 of 313
Which part of the star is the hottest?
264 of 313
Where does most of the fusion take place in a star? Why?
In the core. The pressure from the weight of the rest of the star makes the core hotter and denser than the rest of the star. This means the nuclei are close enough together to fuse.
265 of 313
What happens to the energy that is created by fusion in the core?
It is transported by photons of radiation and convection currents to the photosphere.
266 of 313
What happens to the energy at the surface of a star?
It is radiated into space.
267 of 313
Complete the sentence. The more massive the star...
The hotter its core and the heavier the nuclei it can create by fusion.
268 of 313
When do all stars change?
When there is not enough hydrogen to fuse to make helium.
269 of 313
What happens when the hydrogen runs out?
The core shrinks, the rest of the star expands and the photosphere cools.
270 of 313
What happens to small stars next?
They become a Red Giant.
271 of 313
What happens to the big stars?
They become a Red Supergiant.
272 of 313
What is happening in a Red Giant and Red Supergiant?
The core is compressed by the surrounding matter of the star and shrinks until the pressure and temperature of the core is high enough for helium fusion to begin. The star releases energy by fusing helium into larger nuclei like carbon, nitrogen+oxy.
273 of 313
What does a Red Giant become? How? (Part 1)
A Red Giant becomes a White Dwarf. Once there is too little helium to fuse, the core becomes unstable and it's compressed by the rest of the star. A Red Giant doesn't have enough mass to compress the core, so no more nuclear fusion occurs.
274 of 313
What does a Red Giant become? How? (Part 2)
The outer layers of the star are thrown off into space and the core shrinks to become a hot white dwarf. In white dwarf stars there is no nuclear fusion so the star gradually cools and fades.
275 of 313
What does a Red Supergiant become? How? (Part 1)
The core turns to mostly iron. A Red Supergiant does have enough mass to increase the pressure and temperature of the core enough to fuse larger nuclei.
276 of 313
What does a Red Supergiant become? How? (Part 1)
Each time an element in the core becomes depleted, the core shrinks until it is hot enough and at a high enough pressure for further fusion to occur. This happens until most of the core has been fused to make iron.
277 of 313
What happens now to a big star?
Red Supergiants cannot fuse iron, so the core collapses and the star explodes as a supernova - creating nuclei with masses greater than iron.
278 of 313
What happens next?
The core collapses to form a neutron star, or if there's enough matter, a black hole from which even light can't escape.
279 of 313
What is the Hertzsprung-Russell Diagram?
A graph that plots temperature and luminosity of stars.
280 of 313
How are the stars arranged in this diagram?
Different types of stars are grouped together in distinct areas.
281 of 313
What do the different areas show you?
The main stages of a star's life cycle: The main sequence, red giants and supergiants and white dwarfs.
282 of 313
Why can we see these areas?
Stars exist in these stable stages of their life cycle for long periods of time.
283 of 313
Give an example of an unstable stage.
284 of 313
Why don't we see unstable stages on the diagram?
Because they happen too quickly.
285 of 313
What are the advantages of using a computer controlled telescope? (Part 1)
1.The astronomer doesn't always have to be with the telescope, they can just program the telescope to track an object in the sky.
286 of 313
What are the advantages of using a computer controlled telescope? (Part 2)
2.Computer controlled telescopes can be programmed to constantly repositioned when doing a survey that involves studying large areas of the night sky. 3.They allow telescopes to be positioned more precisely.
287 of 313
What are the advantages of using a computer controlled telescope? (Part 3)
4.Telescopes can be put in remote places without the astronomer having to travel there to collect the data. 5.Computers can record and process data from telescopes.
288 of 313
Where do Scientists think the necessary conditions for life are most likely to be found?
On other planets or moons.
289 of 313
What evidence have they found to suggest there is other life in the universe?
There is evidence for planets orbiting around hundreds of nearby stars.
290 of 313
What do scientists believe?
Even if only a small proportion of stars have planets orbiting them, there is still a chance of extraterrestrial life.
291 of 313
Has any evidence been found of extraterrestrial life?
No, so far there's no evidence that any extraterrestrial life exists or has existed in the past.
292 of 313
What do astronomers need in order to understand what's going on in space?
293 of 313
Why is this not always possible?
The atmosphere can ruin the results.
294 of 313
How does the atmosphere do this?
Our atmosphere only lets certain wavelengths of electromagnetic radiation through and blocks all others.
295 of 313
Which radiation does the atmosphere let through?
It lets through radio waves.
296 of 313
What radiation is badly affected by the atmosphere? How?
Visible light. Light gets refracted by water in the atmosphere, which blurs the images. It can also be absorbed by the dust particles in the air.
297 of 313
What is one solution to this problem?
Choosing sites for astronomical observatories on Earth very carefully to try and minimise all of these problems.
298 of 313
What is another solution?
Using space telescopes.
299 of 313
What are the advantages of using space telescopes?
1.You can look at the EM radiation that is blocked or affected by the atmosphere. 2.It avoids absorption and refraction affects of light in the atmosphere.
300 of 313
What are the disadvantages of using space telescopes?
1.They are a lot more expensive to and harder to build, maintain and repair than Earth-based telescopes. 2.Space programmes have uncertainties.
301 of 313
What are the uncertainties of space programmes? (Part 1)
1.They are extremely expensive. 2.Governments have to balance paying for space programmes with paying for things like defence, healthcare and coping with natural disasters. This means there could be cut-backs at any time.
302 of 313
What are the uncertainties of space programmes? (Part 2)
3.Many countries space programmes are linked so a cut-back in one country can have a knock-on effect in other countries.
303 of 313
Where are most of the world's optical and infrared observatories situated?
Hawaii, Chile, Australia and the Canary Islands.
304 of 313
Why do countries work together in astronomical research?
1.It is too expensive for one country to carry out. 2.You can get the best people and the best facilities for the job.
305 of 313
Give an example showing how international cooperation is essential for progress in astronomy.
1.The International Space Station is a project led by the US with the help of 15 other countries. Each country is providing different parts of the Station and it's the largest and most expensive international science project in industry.
306 of 313
Give another example showing how international cooperation is essential for progress in astronomy.
2.The European Extremely Large Telescope is a project involving astronomers from across the whole of Europe, but based in Chile. It's too complex and expensive for a single country to build and operate.
307 of 313
Describe the astronomical factors that influence the choice of the site for major astronomical observatories. (Part 1)
1.Distant from built up areas that cause light pollution which affects the observations. 2.High elevation to decrease the amount of atmosphere between the observatory and the telescopes to minimise any blurring effects it has.
308 of 313
Describe the astronomical factors that influence the choice of the site for major astronomical observatories. (Part 2)
3.Low atmospheric pollution and dry air to stop the water in the atmospshere from refracting the light. 4.Frequent cloudless nights so that clouds do not block the view of the telescope.
309 of 313
Describe the non-astronomical factors that need to be taken into account. (Part 1)
1.Cost - Transporting the materials to remote places is very expensive. There's the cost of building, running and eventually closing the observatory. 2.Access - The site will have to have roads built to it as well as electricity and other facilities.
310 of 313
Describe the non-astronomical factors that need to be taken into account. (Part 2)
3.Environmental - Scientists have to be careful that building works, etc. will damage the surrounding environment as little as possible, eg. by disturbance to wildlife or agriculture.
311 of 313
Describe the non-astronomical factors that need to be taken into account. (Part 3)
4.Social - Workers need facilities such as water, electricity, accommodation, shops, etc., which will be quite expensive to provide.
312 of 313
Explain how some observatories have benefited the local community.
By providing jobs in building and maintaining the observatory.
313 of 313
Other cards in this set
How long does it take the Moon to orbit the Earth?
How long does it take the Earth to rotate once on its axis?
What is a sidereal day?
How long is a sidereal day?
Similar Physics resources: