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Physics > Topic 4:Waves And Electromagnet > Flashcards

Topic 4:Waves And Electromagnet Flashcards

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1
Q

What do all waves transfer?

A

Energy and information from one place to another

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2
Q

What do waves not transfer?

A

Matter!

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3
Q

What are the 2 types of wave?

A

Transverse and longitudinal

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4
Q

What does a transverse wave do?

A

Used to show wave length and amplitude

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5
Q

How do the particles in a transverse wave move?

A

Each particle moves at a 90° angle, perpendicular to the direction of motion

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6
Q

Examples of transverse waves

A

Sea waves, secondary earthquake waves

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7
Q

What do longitudinal waves show?

A

Show areas of compression and refraction

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8
Q

How do the particles in longitudinal waves move?

A

They can oscillations parallel(in the same direction) to the direction of motion

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9
Q

Examples of longitudinal waves

A

Sound

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10
Q

What is the frequency and what’s the measurement?

A

Number of waves passing a point each second, measure in Hz

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11
Q

What does wavelength mean and measurement?

A

Distance from one point on a wave to the same point on the next wave, m

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12
Q

What is the amplitude and measurement?

A

Distance from the middle of the wave to the the top or bottom, m

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13
Q

What is the period and measurement?

A

The length of time it takes one wave to pass a certain point, seconds

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14
Q

What is the velocity and measurement?

A

The speed of a wave in the direction it’s travelling, m/s

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15
Q

What happens if the frequency increases?

A

The wavelength decreases

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16
Q

High frequency =?

A

Higher pitch

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17
Q

What is the equation for speed?

A

Speed = distance/time

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18
Q

What is the equation for wave speed?

A

Wave speed(m/s) = frequency(Hz) X wavelength(m)

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19
Q

What is refraction?

A

The bending of a wave when it enters a medium where it’s speed is different

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20
Q

What depends on the density?

A

The medium changing the speed of the wave

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21
Q

Where is the normal line?

A

At 90° angle to the interface

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22
Q

The higher the density =?

A

The slower the wave travels

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23
Q

Normal =?

A

Perpendicular to the surface

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24
Q

Less dense means?

A

Away from the normal

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25
Q

More dense means?

A

Towards the normal

26
Q

What happens to the frequency?

A

It always stays the same

27
Q

If the speed increases what happens to the wavelength?

A

It increases

28
Q

What is an example of a water wave that shows the particles vibrate and transfer information but don’t move

A

If u drop a twig into a calm pool of water, ripples form on, and move across the waters surface, the ripples don’t carry the water or the twig away from them tho

29
Q

What is an example of a sound wave that shows the particles vibrate and transfer information but don’t move

A

If u strum a guitar string and create a sound wave, the sound wave travels to your ear but it doesn’t carry the air away from the guitar

30
Q

What does an oscilloscope measure

A

The speed of a sound

31
Q

Steps of using an oscilloscope to measure the speed of sound

A

1) set up the oscilloscope so the detected waves at each microphone are shown as separate waves
2) start with both microphones next to the speaker, then slowly move one away until the 2 waves are aligned on the display but have moved exactly 1 wavelength apart
3) measure the distance between the microphones to find 1 wavelength
4) use the formula velocity=wavelength x frequency to find the speed of the sound waves passing thru the air - frequency is whatever u set the signal generator to in the first placem

32
Q

What do u use to find the wavelength of sound waves generated

A

2 microphones and an oscilloscope

33
Q

What do u use to measure the speed of water ripples

A

A strobe light

34
Q

What are the steps to measuring thr speed of water ripples using a strobe light

A

1) using a signal generator attached to the dipper of a ripple tank u can create water waves at a set frequency
2) dim the lights and turn on the strobe light - you’ll see a wave pattern made by the shadows of the wave crests on the screen below the tank
3) alter the frequency of the strobe light till the wave pattern freezes - when frequency of strobe light and wave are =
4) distance between each shadow line is equal to 1 wavelength. Measure the distance between lines that are 10 wavelengths apart = average wavelength
5) calc speed of the waves

35
Q

How do u find the speed of waves in solids

A

Use peak frequency

36
Q

How do u use peak frequency to measure the speed of waves in solids

A

1) measure and record the length of a metal rod e.g. brass rod
2) set up apparatus with clamp, elastic bands hammer, microphone, rod. Make sure to secure the rod at its centre
3) tap the rod with the hammer. Write down the peak frequency displayed by the computer
4) repeat this 3 times to get an average peak frequency
5) calc the speed, wavelength = twice length of the rod

37
Q

What 3 things can happen when a wave meets a boundary

A

Can be absorbed by the 2nd material, transmitted thru the 2nd material or reflected

38
Q

What does it mean if the wave is absorbed by the 2nd material

A

The wave transfers energy to the materials energy store often the energy is transferred to a thermal energy store which leads to heating

39
Q

What do3s it mean if the wave is transmitted thru the 2nd materia

A

The wave carried on travelling thru the new material this often leads to refraction this can be used in communications as well as in the lenses of glasses and cameras

40
Q

What happens when a wave crosses a boundary between different materials

A

It changes speed

41
Q

What happens if the wave hits the boundary at an angle

A

This change of speed causes a change in direction-refraction

42
Q

What type of waves are electromagnetic waves

A

Transverse

43
Q

What speed do electromagnetic waves travel through a vacuum

A

The same speed

44
Q

What do all EM waves transfer and e.g.

A

Energy from a source to an absorber, e.g. when u warm yourself by an electric heater, infrared waves transfer energy from the thermal energy store of the heater(source) to your thermal energy store(absorber)

45
Q

What is the order of EM spectrum

A

Radio waves, micro waves, infrared, visible light, ultra violet, X-rays, gamma rays

46
Q

What does the higher the frequency of the EM wave mean

A

The more energy it transfers so the more dangerous for humans

47
Q

What are the harmful effects on humans of microwaves

A

Internal heating of body cells

48
Q

What are the harmful effects on humans of infrared

A

Skin burns

49
Q

What are the harmful effects on humans of UV rays

A

Ionising radiation - damages surface of cells and eyes leading to skin cancer and eye conditions

50
Q

What are the harmful effects on humans of x-rays and gamma rays

A

Mutation or damage to cells in the body

51
Q

Uses of radio waves

A

Broadcasting, communications, satellite transmissions

52
Q

Uses of microwaves

A

Cooking, communications, satellite transmissions

53
Q

Uses of infrared

A

Cooking, thermal imagery, short range communications, optical fibres, television remote controls, security systems,

54
Q

Uses of visible light

A

Vision, photography, illumination

55
Q

Uses of ultra violet

A

Security marking, fluorescent lamps, detecting forged bank notes, disinfecting water

56
Q

Uses of x-rays

A

Observing internal structure of objects, airport security scanners, medical x-rays

57
Q

Uses of gamma rays

A

Sterilising food and medical equipment, detection of cancer and it’s treatment

58
Q

What can radio waves be produce by and induce

A

Oscillations in electrical circuits

59
Q

What can changes in atoms and nuclei do

A

Generate radiation’s over a wide frequency range, be caused by absorption of a wide range of radiations

60
Q

How are EM waves grouped

A

Based on their wavelength and frequency

61
Q

What are EM waves made up of

A

Oscillating electric and magnetic fields

Physics (7 decks)

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