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Physics IGCSE > 3 - Waves > Flashcards

3 - Waves Flashcards

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1
Q 
angle = ?
frequency = ?
wavelength = ?
velocity = ?
time = ?
A 
angle = degree (°) 
frequency = hertz (Hz)
wavelength = metre (m)
velocity = metre/second (m/s)
time = second (s)
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2
Q

What do all waves have in common?

A

All waves transfer energy from one place to another

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3
Q

What is an oscillation?

A

The wave is moving up and down. Scientists call these movements oscillations.

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4
Q

What are transverse waves?

A

A wave that vibrates or oscillates at right angles (perpendicular) to the direction in which energy is transferred/ the wave is moving.
The oscillations are up and down but the direction of energy transfer is sideways.
example: Light

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5
Q

What are longitudinal waves?

A

The oscillations are parallel to the direction of energy transfer. All longitudinal waves require a medium to travel in e.g. a liquid, air or a solid.
Examples are soundwaves travelling through the air. Sound waves travel as particles in the air move from side to side.

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6
Q

What is the frequency?

A

number of waves that pass a certain point per second. (Higher frequency waves have shorter wavelengths). It is measured in Hz, 1 Hertz = 1 wave per seconds

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7
Q

What is the wavefront?

A

Created by overlapping lots of different waves. A wavefront is where all the vibrations are in phase and the same distance from the source.

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8
Q

What are compressions and what are rarefactions?

A

compressions: regions in the longitudinal waves where the air particles are very close together
rarefactions: regions in the longitudinal waves where the air particles are spaced out

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9
Q

What is Amplitude?

A

The maximum (furthest) displacement of a point n a wave away from its undisturbed position

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10
Q

What is the crest/peak and what is the trough?

A

Crest/peak: The highest surface part of a wave is called the crest
trough: the lowest part is the trough

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11
Q

What is wavelength?

A

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

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12
Q

What is the special symbol for wavelength?

A

λ (lambda)

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13
Q

How do you measure the wavelength of longitudinal waves?

A

Measure wither one compression to the next compression or from one rarefaction to the next

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14
Q

What is the period of a wave? What is the equation?

A

The period is the time (in seconds) for one wave to pass a point.
1 1
period(s) = ———————— T = —
frequency (Hz). f

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15
Q

Do waves transfer matter when transferring energy and information?

A

Waves can transfer energy and information without transferring matter, For example, when we drop a pebble into a pond, a few circular ripples move outward on the surface of the water. As the ripples spread outward, any object on the surface of the water (e.g. a leaf) would only bob up and down, not moved. This shows that waves transfer energy without transferring any matter! (The leaf bobs up and down because water waves are transverse.)

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16
Q

What is the relationship between the speed, frequency and wavelength of a wave?

A

wave speed=frequency x wavelength

v= f x λ

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17
Q

What is the relationship between frequency and time period?

A

1 1
period(s) = ———————— T = —
frequency (Hz). f
So a higher frequency implies that more waves are produced in one second. This means that the period T will be shorter.

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18
Q

What happens to the frequency and wavelength when thinking is travelling towards or away from you?

A

Away:

  • frequency: decrease
  • wavelength: increase

Towards:

  • frequency: increase
  • wavelength: decrease
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19
Q

Exam question: Explain what happens o the sound emitted by a siren on a police car if it were to travel towards and past you.

A

As the car travels towards you:

  • frequency of the waves increases (more high pitch) (1)
  • wavelength of the waves decreases (1)

as the car travels past you:

  • frequency of the wave decreases (lower pitch) (1)
  • wavelength of the wave increases (1)
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20
Q

can all waves be reflected and refracted?

A

Yes

21
Q

What is the Electromagnetic Spectrum? Is light a part of it?

A

A continuous spectrum of waves of differing frequencies.
All electromagnetic waves have the following properties:
- Transfer energy
- Are transverse waves
- Travel at the speed of light in a vacuum
- Can be reflected and refracted

Yes, Light is part of the electromagnetic spectrum.

22
Q

What is the order of the electromagnetic spectrum in order of increasing frequency, lowest at the to and decreasing wavelength, lowest at the bottom.

A 
Radio Waves
Microwaves
Infrared (IR)
Visible Light
Ultraviolet (UV)
X – Rays
Gamma Ray

Rich, Men, In, Vegas, Use, eX, Girlfriends

23
Q

What is the speed of light in air?

A

3×10^8 m/s

24
Q

What are some uses of radio waves?

A

broadcasting and communications

25
Q

What are some uses of microwaves?

A

cooking and satellite transmissions

26
Q

What are some uses of infrared waves?

A

heaters and night vision equipment

27
Q

What are some uses of visible light?

A

optical fibres and photography

28
Q

What are some uses of ultraviolet waves?

A

fluorescent lamps

29
Q

What are some uses of x-ray?

A

observing the internal structure of objects and materials, including for medical applications

30
Q

What are some uses of gamma rays?

A

sterilising food and medical equipment.

31
Q

What are some of the detrimental effects of excessive exposure of the human body to radiowaves?

A

Radiowaves probably don’t cause harm to human bodies.

32
Q

What are some of the detrimental effects of excessive exposure of the human body to microwaves?

A

internal heating of body tissue

33
Q

What are some of the detrimental effects of excessive exposure of the human body to Infrared waves?

A

Can cause surface burns to the skin (skin burns not ‘sunburn’)

34
Q

What are some of the detrimental effects of excessive exposure of the human body to visible?

A

Can cause visual impairment

35
Q

What are some of the detrimental effects of excessive exposure of the human body to Ultraviolet? How can this be avoided?

A

damage to surface cells and blindness

avoided:
- wear sun glasses, sun cream and stay in shade for UV

36
Q

What are some of the detrimental effects of excessive exposure of the human body to x-rays? How can this be avoided?

A

Can mutate/kill cells inside the body

avoid:
- Avoid exposure.

37
Q

What are some of the detrimental effects of excessive exposure of the human body to gamma rays? How could this be avoided?

A

mutate/kill cells inside the body. Cause cancer

avoid:
- Wear led clothing for Gamma

38
Q

What does reflected mean?

A

Light will “bounce” back from the surface (at the same angle that they hit the surface)

39
Q

What does refracted mean?

A

Light waves change speed when enters another medium of a different density. This causes them to change direction.

40
Q

What does diffracted mean?

A

When light meets a barrier, it will carry on through a gap and spread out in the area beyond.

41
Q

What is light in terms of waves?

A

light is a transverse wave that can be reflected, refracted and diffracted.

42
Q

What is the equation for the law of reflection?

A

angle of incidence (i) = angle of reflection (r)

43
Q

How do you draw a virtual image?

A
  1. First draw a line from the object which crosses the mirror at right angles
  2. Mark the image the same distance behind the line as the object is in front of the line
  3. Now draw 2 rays coming from the image which crosses the mirror. The rays should be dotted behind the mirror and solid in front of the mirror. Don’t forget to put arrows on the lines to show that they are coming from the image.
  4. Now connect the points at which the rays crosses the mirror to the object.
  5. Now add normals at right angles to the mirror where the rays bounce off it. Mark the angles of incidence and reflection- which should be identical
  6. Finally draw an eye to show where the virtual image is being viewed from.
44
Q

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

A

… . .. . . . .. .. . . sin(angle of incidence). sin(i)
refracted index = ———————————— n = ——–
sin(angle of refraction). sin(r)

45
Q

What is total internal reflection and why is it used when transmitting information along optical fibres and in prisms?

A

Light is refracted, a fraction of light is reflected.
When total internal reflection occurs, all light is reflected, and none is refracted.

Total internal reflection is used when transmitting information along optical fibres and in prisms because light travels at the speed of light (300 million m/s). No information will be lost in refracting rays.

46
Q

What are the 2 conditions needed for total internal reflection?

A
  • Angle of incidence must be greater than the critical angle

- Light must be travelling from a dense medium, to a less dense one (higher refractive index, to a lower one)

47
Q

What is the critical angle?

A
  • When light travels from one medium to another it is refracted; it changes angle due to change in density.
  • Past a certain angle the light will simply be refracted back into the medium it is in, this angle is the critical angle.
  • At a certain angle, the critical angle c, the light will be refracted so that is goes along the surface of the material; here the angle of refraction is 90°.
  • If light hits the surface at a greater angle than this it will not escape the material but instead will totally reflected. total internal reflection.
48
Q

What does the diagram look like then the angle of incidence is less than the critical angle?

A
  • the light is refracted because Θi < Θc
49
Q

What does the diagram look like then the angle of incidence is greater than the critical angle?

A
  • total internal reflection because Θi > Θc

Physics IGCSE (9 decks)

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