# Section 3- Waves Flashcards

1
Q

What is the use of hertz

A
• used for frequency

- the number of cycles per second of something which repeats regularly

2
Q

What are transverse and longitudinal waves?

A
• in a transverse wave, the displacements (certain points on the wave moving) /oscillations/ vibrations are perpendicular ( at right angles) to the direction of energy transfer (e.g light waves and waves seen in water)- these waves can be demonstrated on springs (springs can also demonstrate longitudinal)
• in longitudinal waves, the displacements/oscillations/vibrations are parallel (in the same direction) as the direction of energy transfer. E.g sound waves are longitudinal

BOTH TRANSFER ENERGY

3
Q

What is the period of a wave?

A

(Time) period for one wave to pass a point- different to frequency which is how many waves pass a point in an amount of time
MEASURED IN SECONDS

4
Q

How is the (time) period of a wave calculated?

A

T=1/frequency

5
Q

What is the frequency of a wave?

A

-The number of waves that pass a point in one second e.g. if two waves pass a point in one second the frequency would be 2Hz
MEASURED IN HERTZ (Hz)

6
Q

What is the amplitude of a wave?

A

The maximum disturbance of a wave from the equilibrium

7
Q

What is the equilibrium of a wave?

A

The horizontal midpoint of a wave

8
Q

What is wavelength?

A

The distance between a particular point on one wave and the same point on the next wave

9
Q

What is the compression of a wave?

A

The more dense part of a longitudinal wave

10
Q

What is the rarefraction of a wave?

A

The less dense part of a longitudinal wave

11
Q

What is the crest on a wave?

A

The highest point on a transverse wave form

12
Q

What is the trough on a wave?

A

The lowest point on a transverse waveform

13
Q

How does energy travel?

A
• without particles or transfer of matter
• some waves travel without the use of particles at all, e.g light (electromagnetic) waves
• others cause particles to vibrate, but eventually return to their original position
• we call the material that a wave passes through a ‘medium’
14
Q

How do we calculate the wave speed of a wave?

A

Speed=frequency x wavelength

OR

v=f x (lambda sign)

15
Q

what is m/s ^-1 the same as?

A

M/s

16
Q

What is the Doppler effect?

A
• the idea that a moving object emitting waves had bunched waves with a higher frequency in front of it, and mor spread out waves behind it with a lower frequency
• e.g as an ambulance moves towards you, the pitch is higher, then as it moves past and away from you, the pitch becomes lower
17
Q

What is redshift?

A
• red shift is the same idea as the Doppler effect, but with light. From our perspective, Galaxies moving towards us have compressed wavelengths and therefore their wavelengths are shifted to the blue end of the spectrum. If it is moving away from us then the wavelengths are shifted to the red end of the spectrum
• The amount of redshift is dependant on the speed at which the galaxy is moving to/away from us
• on the whole, we can see that most galaxies are moving away from us, proving that the universe is expanding
• we can also see that universes further away from us are moving faster
18
Q

How are waves reflected?

A
• all waves can be reflected.
• if they hit a straight/flat barrier, the angle at which they leave the barrier surface is equal to the angle at which they ,set the surface
• the reflected wave is also the same distance from the normal as the original wave
• the angle of incidence is the angle of the original wave from the normal
• the angle of reflection is the angle of the reflected wave from the normal
• the direction of the reflected wave is away from the barrier
19
Q

How are waves refracted?

A
• if a ray moves from a less dense medium to a more dense medium, the ray will be refracted towards the normal
• if a ray travels from a more dense medium to a less dense medium, it will be refracted away from the normal
• if the ray enters the glass block at 90 degrees (ie along the normal) so it has an angle of 0 degrees from the normal, it will not refract and it will pass straight through
20
Q

What are the components of the electromagnetic spectrum? In order

A

Radio, microwave, infrared, visible light, ultra violet, x-rays, gamma

21
Q

Which wave in the electromagnetic spectrum has the lowest/highest wavelength/frequency

A

Wavelength: radio waves have the longest, gamma rays have the shortest
Frequency: radio waves have the lowest, gamma rays have the highest

22
Q

What is the speed of the electromagnetic waves in free space (vacuum)

A

they are the same

23
Q

What colours is white light made up of?

A

All the colours of the visible spectrum

24
Q

Which colour light has the longest wavelength?

A

Red light

25
Q

Which colour light has the shortest wavelength?

A

Violet

26
Q

What are the colours in the electromagnetic spectrum from long to short wavelength?

A

Red, orange, yellow, green, blue, indigo, violet

27
Q

What are the uses for radio waves?

A

28
Q

What are the uses for microwaves

A

Cooking and satellite transmissions

29
Q

What are the uses for infrared radiation?

A

Heaters and night vision equipment

30
Q

What are the uses for visible light?

A

Optical fibres and photography

31
Q

What are the uses for ultraviolet?

A

Fluorescent lights

32
Q

What are the uses for x-rays?

A

Observing the internal structure of objects and materials and medical applications

33
Q

What are the uses for gamma rays?

A

Sterilising food and medical equipment (through wrapping/packaging)

34
Q

What are the detrimental effects of excessive exposure to microwaves?

A

Internal heating of body tissues

35
Q

What are the detrimental effects of excessive exposure to infrared radiation?

A

Skin burns

36
Q

What are the detrimental effects of excessive exposure to ultraviolet? And how can you protect yourself from this?

A

Damage to surface cells and blindness- suncream sunglasses clothing

37
Q

What are the detrimental effects of excessive exposure to gamma rays? And how can you protect yourself from this?

A

Cancer, mutation- when killing cancer cells inside a persons body the source of gamma radiation focuses in a circle around the patient’s body. the cancer cells are at the centre of the circle so the gamma rays hit the cancer cells all of the time

38
Q

What kind of wave is a light wave?

A

Transverse

39
Q

What is the law of reflection?

A

The angle of incidence equals the angle of reflection

40
Q

What is refraction?

A
• occurs when light rays travel from one medium to another e.g. from air into glass
• we say refraction occurs at the boundary between media
• all waves can refract
41
Q

What is the relationship between refractive index angle of incidence and angle of refraction?

A

N (refractive index) = sin i / sin r

42
Q

What is the refractive index of glass?

A

1.5

43
Q

What is meant by the critical angle of a material?

A

The minimum angle at which total internal reflection occurs

44
Q

What is meant by total internal reflection?

A

Where a ray is incident at a Boundry rather than crossing the Boundry and being reflected

45
Q

What is the role of total internal reflection in transmitting information along optical fibres and in prisms

A

-Each light ray entering a fibre at one end of an endoscope leaves the fibre at the other end, even if the fibre bends round because of total internal reflection each time the ray reaches the fibres Boundry

46
Q

What is the relationship between critical angle and refractive index?

A

Sin c= 1/n

OR

sin (critical angle) =1/refractive index

47
Q

What is the frequency range for human hearing?

A

20Hz to 20,000 Hz

48
Q

What is a wavefront?

A

The plain which which connects all the adjacent points of 2 or more waves

49
Q

What are the uses of total internal reflection?

A
• optical fibres

- bike reflectors

50
Q

What substances can/cannot radio waves pass through

A

Can: walls, trees, buildings, land (dry, non-metals)

Can’t: water, metals (these absorb radio waves)

51
Q

What are radio waves reflected by in order to send information?

A

One of the Earth’s atmospheres

52
Q

What things absorbs microwaves

A

Water (e.g in food)

53
Q

What reflects microwaves?

A

Metals

54
Q

Which microwaves are used to carry information to and from satellites?

A

Microwaves which can pass through the earths atmosphere

55
Q

A

Yes

56
Q

A

Shiny surfaces

57
Q

What absorbs ultraviolet (UV) rays?

A

The atmosphere

58
Q

What reflects ultraviolet (UV) rays?

A

White and shiny surfaces

59
Q

What do X-rays not pass through?

A

Bones and diseased tissue

60
Q

Why do metals protect your body from X-rays?

A

They absorb x rays

61
Q

How does photographic film work?

A
• x-rays can pass easily through skin and flesh but not through bone/diseased tissue
• photographic film absorbs any x-rays which fall onto it
• these parts of the film go dark when the film is developed
62
Q

How do gamma rays sterilise medical equipment/keep food fresh?

A

-they can easily pass through any wrapping, so you don’t have to open packaging, adding bacteria

63
Q

What is meant by the term refraction

A

The change in direction of a ray passing through a medium with a change in density