# Physics P1

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How does energy flow?
From hot to cold objects
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What does a thermogram show?
It shows colour using temperature
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What is temperature?
a measure of hotness
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On what scale is temperature measured in?
an arbitrary scale
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What happens when the temperature increases?
the average kinetic energy of the particles inceases
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What is heat a measurment of?
internal energy
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What is specific heat capacity?
The amount of energy needed to raise the temperature of 1KG of material by one degree celsius
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What is specific latent heat?
The amount of energy needed to melt or boil 1KG of material
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Why does the temperature stay the same when a material changes state?
Because the energy is needed to break bonds.
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How does double glazing reduce energy loss?
By conduction
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Explain how loft insulation reduces energy loss
By conduction and convection. The warm air rises and energy is transferred by conduction, The loft air is warmed and can be moved by conduction outside from the roof tiles
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How can energy transformations be shown?
By a sankey diagram
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What is the amplitude of a wave?
The maximum displacement from its rest position
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What is the crest and trough of a wave?
The crest is the highest point from the rest position, and the trough is the lowest.
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What is the wavelength?
The distance between two successive points.
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What is the frequency of a wave?
The number of complete waves passing a point in one second.
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Name all of the waves in the electromagnetic spectrum.
Radio, microwave, infrared, visible, ultraviolet, x-ray, gamma ray
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Why does refraction occur?
Because the speed of the wave decreases as it passes through a more dense medium
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What is diffraction?
The spreading of waves as it passes through a gap
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What does the amount of diffraction depend on?
The size of the gap
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What is the morse code an example of?
A digital signal
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What is the best benefit of sending a signal by light, electricity, microwaves or radio?
It is almost instant
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What is white light made from?
different colours of different frequencies that are out of phase
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what usually happens when light travels from one material to another?
it is refracted
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What happens if the light is passing from a more dense to a less dense material?
The angle of refraction is bigger than the angle of incidence
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What is the angle of incidence called if the angle of refrction is 90 degrees?
the critical angle
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How does an endoscope work?
Light passes along one set of optical fibres to illuminate the inside of the body, the light is reflected, and it travels along a different set of optical fibres to a camera
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How far can microwaves penetrate food?
1cm
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How does a normal oven cook food by infrared radiation?
The energy is absorbed by the surface of the food, then the kinetic energy inceases, and the rest of the food is heated by conduction
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How long can microwave waves be?
1mm-30cm
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How are satellites used for microwave communication?
The signal from earth is recieved and re-transmitted back to earth.
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Why do scienctists publish their results?
So others can test their findings
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How does a remote work?
The button is pressed, which completes a circuit. A message is sent and a light transmits pulses, indicating whether to change the channel or the volume.
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Why is digital TV better than analogue?
The signal is better, you get a greater choice of programms, and you can get extra services such as subtitles.
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How do optical fibres work?
They allow information to be transmitted by pulses of light.
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Why is interference in digital signals not a problem?
Because there are only two values
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What happens to the interference if the wave has been amplified?
The interference will also be amplified
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What allows a number of digital systems to be sent at the same time?
multiplexing
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What is wireless technology used by?
Laptops, PC's, and mobile phones
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What are radio waves reflected and refracted by?
The earths atmosphere
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How can the same frequency be used for different radio stations?
If the radio stations are far away.
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Where are radio waves reflected from?
The ionosphere
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What does water reflect?
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What wave can pass through the ionosphere?
microwaves
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What happens to radio waves when they are obstructed?
they are diffracted
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What does a seismograph show?
The different types of earthquake waves
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What are the three types of waves?
L, P, S
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What do L waves do?
Travel around the surface very slowly
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what are P waves and what do P waves do?
They are longitudal pressure waves, and they travel through the earth at 5-8 KM/S
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What are S waves and what do they do?
They are traverse waves, and they travel through the earth between 3-5.5 KM/S
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What happens to P waves when they travel through the earth?
They are refracted by the core
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Why is this helpful for scienctists?
Because they could work out the size of the earths core
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How is a tan caused?
The ultraviolet light on the skin
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Why is it more difficult for darker people to tan?
Because the melanin in their skin absorbs more of the ultraviolet light safetly
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Where is the ozone found?
In the stratosphere
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What is the purpose of the ozone?
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Why is the ozone layer its thinnest at the south pole?
Because the chemicals that damage it have the most effect in colder temperatures
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How do scienctists moniter the thickness of the ozone layer?
Using satellites
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What is the equation for energy transfer by SHC?
energy transferred= mass x SHC X temperature change
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What is the equation for energy transfer by SLH?
energy transferred= mas x specific latent heat
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Why is it impossible to transfer energy through conduction in a vacuum?
Because there are NO particles in a vacuum
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Why is foam cavity wall insulation effective?
because the air in the foam is a good insulator and the air cannot move by convection because it is trapped in the foam.
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How do insulation blocks reduce energy transfer?
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What are the insulation blocks covered in the aid this?
shiny foil on both sides
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How do insulation blocks work?
energy from the sun is reflected back to kkep the house cool in summer, and the energy is reflected back into the house to keep it warm during winter
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What happens when convection occurs?
The gas expands when it heats up, so becomes less dense, so it rises
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What happens when conduction occurs?
kinetic energy is transferred through particles
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What is the equation for Density?
density= Mass / volume
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Why can radiation occurin a vacuum?
Because it doesn't need a material to transfer energy
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When does the most diffraction occur?
When the gap is a similar size to the wavelength
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What is morse code?
a series of dots and dashes that represent the alphabet.
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How many frequencies does a laser have?
one frequency in phase
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Explain the process of laser light reading from the surface of a CD
The surface of the CD is pittes, the pits represent the digital signal, the laser light is shonevonto the CD surface and the difference in the reflection provides the information for the digital signal
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If the angle of incidence is bigger than the critical angle, the light is reflected, what is this called?
total internal reflection
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what are telephone conversations and computer data transmitted along?
optical fibres at the speed of light
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How is energy transferred?
by waves
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what does the amiunt of energy depend on?
depends on the frequency and wavelength of the wave
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Why is less energy transferred using mobile phones, than microwave ovens?
Because mobile phones use longer waves than microwave ovens.
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How do microwave ovens cook food?
by microwave radiation, the water or fat molecules in the outer layers of food vibrate more
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Why are aerials usually situated on the tops of tall buildings?
Because the transmitter and reciever must be in line of sight (of eachother)
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Why can signal strength of mobile phones change over short distances?
Because weather and large areas of water can scatter the signals, the curvature of the earth limits the line of sight so the transmitters and recievers have to be a shorter distance away from eachother.
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What signal carries information that allows digital and electric devices to be controlled?
infrared signals
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What 4 things must a signal include for a remote controller or other device to be successful?
start command, instruction demand, device code, stop command
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Before an analogue signal can be transmitted, what is it added to?
A carrier wave
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What is different about carrier waves?
They are usually higher in frequency
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What does the amount of refraction depend on?
the frequency of the wave. (there is less refraction at higher frequencies)
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What allows radio waves to be recieved from an aerial that is not in line of sight?
The continued reflection by the ionosphere and the ocean.
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How are microwave signals recieved and transmitted?
They are recieved by orbiting satelites, are amplified and retransmitted back to earth.
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Where do communication satelites orbit?
Above the equator
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How long do they take to orbit earth?
24 hours
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What can P waves pass through?
solids and liquids
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What can S waves pass through?
solids
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Why are S waves not detected on the opposite side or the earth to where the earthquake was?
Because S waves cannot pass through liquids
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What does this tell scienctists about the earths core?
That it is liquid
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What pigment causes a tan to occur?
melanin that the cells in the skin produce
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## Other cards in this set

### Card 2

#### Front

What does a thermogram show?

#### Back

It shows colour using temperature

### Card 3

#### Front

What is temperature?

### Card 4

#### Front

On what scale is temperature measured in?

### Card 5

#### Front

What happens when the temperature increases?