P6 - Waves

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  • Created by: MiaT212
  • Created on: 24-11-19 11:37
How do waves move?
Particles in the wave oscillate to and fro about a point
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How do the particles move in a transverse wave?
The direction of the particles is perpendicular (at right angles) to the direction of energy transfer.
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How do the particles move in a longitudinal wave?
parallel to the direction in which the energy is transferred.
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What are longitudinal waves made up of?
Compressions and rarefactions
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Do longitudinal waves need a medium to travel through?
Yes
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Can transverse waves travel through a vacuum?
Yes
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What is the amplitude of a wave?
The maximum height of the wave crest from the midpoint of the wave
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What is the wavelength?
The distance from one crest to the next crest
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What is the frequency of a wave?
The number of waves passing a point in one second (Hz)
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How do you calculate the period of a wave?
1/frequency
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How can you calculate the wave speed?
Frequency (f) x wavelength (lambda)
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What is the incident wave?
The waves travelling towards a barrier or boundary
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Waves at a boundary can be reflected, what happens?
The wave speed, and wavelength is unchanged
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What is the relationship between the ray of incidence and reflection?
They are both equal to each other
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What three things can happen to waves at boundaries?
transmitted, absorbed, totally or partially reflected
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When waves cross a boundary what happens?
The wave speed and wavelength change
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What does the change in speed cause?
refraction, a change in direction.
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If the substance is denser than the wave what happens?
The wave slows down and is refracted more towards the normal.
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What happens if a wave is transmitted at 90 degrees to the boundary?
It is transmitted but not refracted.
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What causes sound?
Mechanical vibrations in a substance
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Why cant sound travel through a vacuum?
Because it is a longitudinal wave and requires a medium.
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When sound is reflected from hard, flat surfaces what is produced?
an echo
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What does the pitch of a sound depend on?
The frequency
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What does the volume of a sound depend on and why?
the greater the amplitude, the greater the energy carried and therefore the volume.
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What frequencies can the human ear detect?
20Hz - 20kHz
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Sound waves with a higher frequency than a human can detect are called what?
Ultrasound waves
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Ultrasound waves reflected at boundaries are timed to calculate what?
Distances
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Why is ultrasound used for medical scanning?
It is reflected between different types of tissues so can scan the eye and kidney
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Why is ultrasound use to scan for babies?
It is non-ionising so it doesn't harm the baby
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When calculating distance with ultrasound what do you need to remember?
To half the answer bc that is the distance there AND back.
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P - waves are what type of waves and can travel through what?
longitudinal and can travel through solids and liquids
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S - waves are what type of waves and can travel through what?
transverse and ONLY solids
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How can S - waves show that the mantle is a solid?
Because the S - waves can pass through it
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How can P waves show that the mantle and inner core have different densities?
They change directions as it is being refracted
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Whats the relationship between wavelength and frequency in the EM scale
Inversely proportional, as wavelength increases, frequency decreases
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What is the order of the EM scale?
Radio, Microwaves, Infrared, Visible, UV, X-rays, Gamma
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Gamma rays have the highest what?
Frequency
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Why are X- rays and Gamma rays dangerous?
Because they are ionising and can knock electrons out of their shells.
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The higher the energy, the higher the what?
frequency
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A mixture of all the different colour in visible light creates what?
White light
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Each colour in Visible light has a different what?
wavelength
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Infrared is emitted by what objects?
all objects
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The greater the what, the more IR emitted?
temperature
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What is Infrared used for?
TV remote signals, inside optical fibres, heat detectors
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What are microwaves used for?
communications, microwave cooking, satellite TV
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How can microwaves be used in communications involving satellites?
microwave transmitters produce wavelengths able to pass through the atmosphere
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What are Radio Waves used for?
radio, TV programmes
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Whats the danger with the greater wavelength waves in the EM spectrum?
They can penetrate skin and are absorbed by tissue causing internal heating
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waves used to carry signals are called what
carrier waves
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why are different radio waves wavelengths used for different things
their wavelengths determine how much info they can carry, how far they can travel and how much they spread
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Why is visible light used in optical fibres?
because the shorter wavelength means it can carry more info
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What are UV waves used for?
security marking, sunbeds
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Why is UV harmful?
Prolonged exposure causes skin burn and cancer and harmful to eyes
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what are x rays used for?
create images of bones and detect crack in metal objects
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what are gamma rays used for?
Kill harmful bacteria, sterilise surgical instruments, kill cancer cells
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Why are gamma rays and X rays dangerous?
They are ionising and can kill living cells.
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What precaution do people working with gamma and x rays take?
They shield themselves with lead, wear a film badge to monitor exposure.
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Why can X-rays view bones and not tissue?
X rays pass thorough tissue but are absorbed by teeth and bones.
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What are high-energy X-rays used for?
killing cancer cells
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What is the normal line in the context of reflection?
a line perpendicular to the mirror
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what is the angle of incidence?
the angle between the incident ray and the normal
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what is the angle of reflection?
the angle between the refelcyed ray and the normal
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Reflection from a smooth surface is called what?
specular reflection
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Reflection from a rough surface is called what?
diffuse reflection
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What is refraction?
The change of direction of any kind of wave as it changes speed at a boundary
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When is the only time light isnt refracted through a boundary?
If it passes through the normal
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What is the angle of refraction?
The angle between the normal and refracted ray
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What happens when a ray passes from a more dense medium to a less dense one?
It speeds up and the angle of refraction is greater than the angle of incidence
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Why would a red shirt appear black in yellow light?
The light would be absorbed and none reflected because there isn't any red light in yellow light
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Why does white appear white?
because it contains no light wavelengths so it reflects them all combining to form white.
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Why does black appear black?
It absorbs all colour and reflects none
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If an object is further away from the lens than the principal focus in a converging lens, what is created?
an inverted, real image
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when is a virtual image formed in a convex lens?
when the image is nearer than the principal focus
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What happens when light passes through a convex lens?
The rays of light are refracted so that they converge at a point called the principal focus
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What is the focal length?
The distance between the from the centre of the lens to the principal focus
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What happens when light passes through a concave lens?
The light rays are refracted so they diverge away from a point
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The image created from a diverging (concave) lens is always what?
Virtual
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What should you always draw on a ray diagram?
The line through the centre of the lens and at right angle to it from the top of the object
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Ray diagrams use how many construction ray from the object to locate the corresponding image?
3
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For a convex lens, the ray at right angle to the object is refracted through what?
the principal focus
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In a convex lens, the lens through the lens travels where?
straight on
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In a convex lens, the ray through the principal focus on the object side is refracted where?
Parallel to the principal axis
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A magnifying glass uses which type of lens?
a converging (convex) lens to produce a virtual, magnified image.
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Other cards in this set

Card 2

Front

How do the particles move in a transverse wave?

Back

The direction of the particles is perpendicular (at right angles) to the direction of energy transfer.

Card 3

Front

How do the particles move in a longitudinal wave?

Back

Preview of the front of card 3

Card 4

Front

What are longitudinal waves made up of?

Back

Preview of the front of card 4

Card 5

Front

Do longitudinal waves need a medium to travel through?

Back

Preview of the front of card 5
View more cards

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