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Eleanor Rowe Physics > Waves > Flashcards

Waves Flashcards

1
Q

What is a wave

A

A vibration of particles that transfer energy

The particles stay in the same place and oscillate (vibrate)

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2
Q

What is frequency

A

The number of waves per second

Measured in Hz

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3
Q

What are transverse waves

A

Sideways vibrations that are perpendicular to the direction of energy transfer

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4
Q

Examples of transverse waves

A

EM waves
Water ripples
Wave on string

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5
Q

What are longitudinal waves

A

Parallel vibrations that are parallel to the direction of energy transfer

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6
Q

Example of longitudinal waves

A

Soundwaves ultrasound and seismic waves

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7
Q

Equation for wave speed

A

Frequency times wavelength

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8
Q

Equation for frequency

A

1/period

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9
Q

What happens when waves arrive at a Boundry

A

They are either
Absorbed by the material and transfer their energy to the material
Transmitted so they keep on travelling
Or reflected

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10
Q

True or false

Angle of incidence = angle of reflection

A

True

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11
Q

What is the normal

A

Align perpendicular to surface at the point of incidence

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12
Q

What is specular reflection and where does it occur

A

When a wave is reflected in a single direction occurs on a smooth surface

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13
Q

What is diffuse reflection and where does it occur

A

It is when the light is scattered in lots of directions because the normal is different for each ray of light
Occurs on a rough surface

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14
Q

Properties of EM waves

A 
Transverse
Transfer energy from source to absorber
All travel at the same speed
All have different frequencies
Form a continuous spectrum
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15
Q

Why do all EM waves have different frequencies

A

They are generated by a variety of changes in atoms and nuclei

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16
Q

What is refraction

A

When waves change direction at a Boundry

It depends on the density of materials

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17
Q

If a wave goes through a material that is more dense, what will happen and why

A

It will have a shorter wavelength and bend towards the normal
Slow down

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18
Q

What happens when a wave goes through a material that is less dense

A

It will have a longer wavelength will speed up and will bend away from the normal

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19
Q

What is optical density

A

How dense and material is and therefore how quickly light can travel through it

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20
Q

What are radio waves

A

Oscillating charges of alternating-current absorbed by receiver

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21
Q

What are long wavelength radio waves used for and how does it work

A

For communication
They bend around curve of earth
They diffract around hills and tunnels

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22
Q

What are short wavelength radio waves used for and how does it work

A

They are reflected by the ionosphere

And transmit Bluetooth signals

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23
Q

What is the ionosphere

A

A charged layer in the atmosphere

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24
Q

How are TV and FM Radio signals sent and what do they have to be

A

They are very short wavelengths

To receive them you must be in direct sight of the transmitter because it doesn’t bend or travel far through buildings

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25
What are microwaves used for and how do they work
Satellites- receive microwaves from transmitters then transmit signals to dish on Earth Food - water in food absorbs microwaves causing the water to heat up which then transfers energy to the rest of the food
26
What is infrared radiation what and what does it do
It is given out by hot objects Detected by infrared cameras The brighter the hotter the object is It cooks food as they absorb the radiation Works as heaters where the wire heats up and current flows through it IR is emitted, making air in room heat up
27
How is visible light used
Used to transmit data and fibre-optic cable is made of glass or plastic where the light reflects off the cable and travels through it so it is not absorbed until received
28
What is UV radiation and how does it work
Radiation absorbed by fluorescent materials that omit light Is very energy efficient Produced by sun making us tan UV lamps give fake tan but are dangerous
29
How are x-rays used in medicine
They show broken bones on a negative image as can’t pass through bone or metal but can pass through flash and aren’t detected
30
How are gamma rays used in medicine
Can kill cancer cells but need to be specifically directed as also kill healthy cells A gamma omitting source for example iodine can be put into the body to show function of thyroid
31
What safety precautions must be taken when using radiation in medicine
The radiographer should wear lead apron, stand behind screen or leave room
32
Are low or high frequency EM waves more harmful and why
High frequency more dangerous | They cause mutations leading to cancer
33
What is a Sievert and what does it measure
Measurement of risk of harm from radiation
34
What do lenses do
Refract light to form images
35
What does diverge and converge mean
Diverge - spread out | Converge - come together
36
In what case would a convex lens produce a virtual image
Of the object is closer than the principle focus
37
Is a magnifying glass concave or convex
Concave
38
How does visible light work
Made up of a range of colours each with a different wavelength the primary colours are red green and blue
39
What happens if all three primary colours are mixed
White light is given off
40
What do opaque objects do to light
Don’t transmit light | Just absorb or reflect it
41
What does the colour of an opaque object depend on
Which wavelengths it most strongly reflects | Eg Apple appears red because it reflects red light the most
42
What wavelengths do white objects reflect
All wavelengths equally
43
What do black objects do to wavelengths of light
Absorb them all
44
What do transparent objects do to light wavelengths
Transmit light
45
What do coloured filters do to visible light
Only let particular wavelengths of light through
46
What do primary colour filters do to light
Only allow that colour wavelength to pas through
47
True or false | All objects continually emit and absorb IR radiation
True
48
What absorbs and emits more IR black or white
Black
49
What absorbs and emits more infrared shiney or Matt
Matt
50
What is black body
An object that absorbs all radiation that hits it | Is the best possible emitter or radiation
51
Why is the earths temp higher in day than night
In day lots of radiation is absorbed from sun | At night less radiation is absorbed
52
What is radiation absorbed or reflected by when coming from the sun to earth
Is absorbed or reflected by clouds
53
What are sound waves
Longitudinal waves caused by vibrating objects
54
Do sound waves travel fastest in solids or liquids
Solids
55
Example of sound waves being produced
Paper diaphragm vibrates causing surrounding particles to vibrate, compressing and rarefracting making sound waves
56
Why can’t sound waves travel in space
There is no particles to vibrate
57
How are sound waves heard by the body
The ear drum vibrates which passes on to the cochlear which sends electrical signals to brain
58
What frequency can humans hear
20-20,000 Hz
59
Do sound waves speed up or slow down in denser material
Speed up
60
What are ultrasound waves and what do they do at boundary’s
They are sound waves with frequency above 20,000Hz | They are partially reflected at boundaries, so can detect how far away an object is
61
Medical use of ultrasound
When reach boundary, some is reflected back and detected | Timing and distribution of echoes is processed by computer to form video
62
Industrial use of ultrasound
Find flaws in object eg pipes | US reflected by far side of object, if flaw or crack present, will be reflected more
63
Why is it important we study the properties of paths of waves
Gives us ideas about structures not seen by the human eye
64
What are seismic waves
Waves produced by earthquake | Detected by seismometers
65
What are P Waves
Waves that travel through solids and liquids Travel faster than S waves Longitudinal
66
What are S waves
Transverse waves Travel through only solids Show outer core is liquid as mine are detected other side of earth after earthquake

Eleanor Rowe Physics (11 decks)

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