# Section 4 - Properties Of Waves Flashcards

1
Q

What is a wave?

A

Wave transfers energy in the direction of travel

2
Q

What is the equation for wave speed?

A

V=f x wavelength

3
Q

Describe a transverse wave?

A

A wave that vibrates perpendicular to the direction of travel

4
Q

What are some examples of transverse waves?

A

5
Q

What is amplitude?

A

The maximum displacement of a point on a wave from into undisturbed position

6
Q

What is wavelength?

A

The distance between the same point on two adjacent waves

7
Q

What is frequency?

A

The number of complete waves that pass a certain point per second

8
Q

Describe a longitudinal wave

A

A wave that vibrates parallel to the direction of travel

9
Q

What is an example of a longitudinal wave?

A

Sound waves

10
Q

What is wave speed?

A

Is the speed at which energy is being transferred

11
Q

What is reflection?

A

Reflection is when a wave bounces off a surface

12
Q

What is the law of reflection?

A

The law of reflection states that the angle of incidence always equals the angle of reflection

13
Q

How can reflection be shown using water waves

A

In a ripple tank a dipper will create waves, when a barrier is places the waves will be reflected

14
Q

What are the two shoes of reflection and explain them

A

Diffuse - when the light hits a bumpy surface and the image is unclear
Spectral - when the light hits a flat surface and the image is clear

15
Q

What is refraction?

A

When waves change direction when passing from one medium to another

16
Q

Why do waves travel differently in different mediums?

A

Due to different densities the way will slow down or speed up

17
Q

What happens when a wave enters a more dense medium?

A

The wave slows down and bends towards the normal

18
Q

What happens when a wave enters a less dense medium?

A

The wave speeds up and bends away from the normal

19
Q

What happens to wavelength and frequency during refraction.

A

Wave speed changes and therefore wavelength or frequency must change
Frequency never changes so wavelength must always change

20
Q

What is dispersion?

A

Dispersion is when white light spreads out into 7 different colours - a rainbow
This is because he different wavelength inside of visible light refract by different amounts

21
Q

What is refractive index?

A

The ratio of the speed of a wave in two different regions

22
Q

What is the refractive index of a vacuum?

A

1

23
Q

What is the equation for refractive index?

A

Refractive index = speed of light in vacuum / speed of light in material

24
Q

What is snells law?

A

It links the equation for refractive index to the angle of incidence and refraction

25
Q

What is snells equation?

A

Refractive index = sin(i) / sin(r)

26
Q

What is total internal reflection?

A

When no refraction occurs and the light is reflected back into the denser medium

27
Q

What are the two criteria for total internal reflection?

A

The rays of light must be going from a more dense to a less dense medium
The angle of incidence must be greater than the critical angle

28
Q

What is the critical angle?

A

The angle of incidence when the ray refracts at a 90 degree angle

29
Q

What id the formula for a critical angle?

A

SinC = 1/n. Or. Sin critical angle = 1 / refractive index

30
Q

How do converging lenses work?

A

Convex lenses that refract the light inwards to a single point

31
Q

How do diverging lenses work?

A

In concave lenses the light is refracted outwards and is dispersed

32
Q

Explain where the principal focus will form.

A

On convex lenses - where the rays meet
On concave lenses - where the rays image meet behind lens
There is a principal focus on both sides, equal distance from the middle

33
Q

What is the name of the distance between the principal focus and the centre of the lens?

A

The focal length - shorter the length the more powerful the lens

34
Q

What is the difference between a real and virtual image?

A

A real image is when the light ray come together whereas a virtual image is when they don’t come together where the image appears

35
Q

How would you describe a real image?

A

Inverted
Real
Smaller

36
Q

How would you describe a virtual image?

A

Virtual
Upright
Smaller

37
Q

What image will a contact lenses make on a ray diagram?

A

A virtual image on the same side of the lens as the object

38
Q

In a convex lens what would happen to the image at different focal lengths?

A

Over 2F - smaller, inverted, real
At 2F - same size, inverted, real
Over 1F - larger, inverted, real
Under 1F - larger, upright, virtual

39
Q

What is the order of the electromagnetic spectrum starting with the smallest?

A

Gamma rays
X rays
Ultra violet
Visible light
Infared
Micro waves

40
Q

What is used to describe visible light of a single frequency?

A

Monochromatic

41
Q

What are some typical uses of radio waves?

A

42
Q

What are some typical uses of microwaves?

A

Mobile phones, microwave ovens

43
Q

What are some typical uses of infared?

A

ELectrical grills, thermal imaging, optical fibres

44
Q

What are some typical uses of visible light?

A

Photography and vision

45
Q

What’s re some typical uses of ultraviolet?

A

Detecting fake items, sterilising water

46
Q

What are some typical uses to X-rays?

A

Medical scanning, security scanning

47
Q

What are some typical uses of gamma rays?

A

Sterilising food and medical equipment , treating cancer

48
Q

What is the speed of electromagnetic waves in a vacuum?

A

3.0 x 10^8 m/s
300,000,000 m/s

49
Q

What is the difference between sections on the electromagnetic spectrum?

A

Different wavelength and frequency

50
Q

In which direction does frequency and wavelength change on the electromagnetic spectrum?

A

Wavelength decreases from radio to gamma
Frequency increases from radio to gamma

51
Q

What can be the region of wavelength for a radio wave?

A

From 1000m to 1m

52
Q

What can be the region of wavelength for a gamma wave?

A

1000th of a nano meter

53
Q

What can be used to see a wave and send it?

A

A transmitter and a oscilloscope and transmitter

54
Q

A

55
Q

What do mobile phones use and why?

A

Microwaves as they can penetrate through walls and only require a short aerial for transmission

56
Q

What are the two types of satellites?

A

Low orbit satellites and geostationary satellites

57
Q

What are the harmful effects of microwaves?

A

Internal heating of body cells

58
Q

What are the harmful effects of infared?

A

Skin burn

59
Q

What are the harmful effects of ultra violet?

A

Damage to skin and eyes leading to skin cancer and eye conditions

60
Q

What are the harmful effects of X-rays or gamma rays?

A

Cell mutation or damage

61
Q

What happens when waves travel through a gap?

A

62
Q

What is diffraction?

A

The spreading out of waves as they ‘bend around’ obstacles

63
Q

What factors effect diffraction?

A

Wave length and gap size

64
Q

What happens when gap size and wavelength change in diffraction?

A

Maximum amount of diffraction when they are equal
Much wider gap is little diffraction
Bit wider gap is diffraction only at edges

65
Q

Explain how Bluetooth uses electromagnetic radiation.

A

Uses low energy radio waves to pass through walls

66
Q

Explain how optical fibres use electromagnetic radiation.

A

Used for cable television and high speed broadband because visible light can carry high rates of data by interpreting the transmission at the other end. Uses total internal reflection

67
Q

What is an analogue signal?

A

They show continuous variation and can take any value within a range

68
Q

What is a digital signal?

A

A signal that can only take a certain value

69
Q

What are the two ways a signal can be transmitted?

A

As a digital or analogue signal

70
Q

What are the benefits of digital signalling?

A

Increased rate if transmission
Increase range of transmission due to more accurate regeneration

71
Q

What is signal regeneration?

A

The process of removing noise from a signal when it is received

72
Q

What is the range of human hearing?

A

20Hz to 20000Hz

73
Q

What is the nature of a sound waves?

A

Longitudinal waves that are caused by vibrating particles

74
Q

Where does sound travel faster?

A

In solids, then liquids then gas

75
Q

What is the speed of a speed of a sound wave in air?

A

350m/s

76
Q

How can you determine speed of sound?

A

Place two microphones a couple metres a way and connect them to a dat logger
Place a sound source on the same line
Measure the distance between the microphones
Find the differnece between time taken to hear sound and divide distance by time

77
Q

How do changes in amplitude effect a sound wave?

A

Amplitude increases with loudness

78
Q

How do changes in frequency effect a sound wave?

A

Higher the frequency the higher the pitch

79
Q

What is an echo?

A

The reflection of a sound wave.

80
Q

What is an ultrasound wave?

A

A sound wave with a frequency greater than 20000Hz

81
Q

What are ultrasound waves used for?

A

Ultrasound scans on babies as can pass through soft tissue and the echo speed can be interpreted by a computer to make visual image

Used to test materials for flaws

Sonar by using echoes