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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

What is wavelength (λ)?

A

The distance from one peak to the next. Measured in metres.

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2
Q

What is frequency (f)?

A

How many complete waves there are per second. Measured in Hz.

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3
Q

What is amplitude?

A

The height of the wave (from rest to crest)

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4
Q

What is period (T)?

A

How many seconds per complete wave. (The time it takes for one complete wave to pass a point)

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5
Q

What is the equation linking frequency and period?

A

f = 1/T

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6
Q

What is the equation linking wavespeed, frequency and wavelength?

A

wavespeed = frequency x wavelength

(m/s) (Hz) (m)

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7
Q

What is a transverse wave?

A

A wave where the vibrations are at 90° to the direction of energy transferred

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8
Q

What is a longitudinal wave?

A

A wave where the vibrations are parallel to the direction of energy transferred

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9
Q

What are two examples of a transverse wave?

A
  • Light and all other EM waves

- Ripples on water

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10
Q

What are two examples of a longitudinal wave?

A
  • Sound and ultrasound waves

- Shock waves

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11
Q

All waves transfer ….. and ….. without transferring …..

A

All waves transfer ENERGY and INFORMATION without transferring MATTER

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12
Q

What are the 7 types of EM wave?

A 
Radio waves
Micro waves
Infrared waves
Visible waves
Ultraviolet waves
X-rays
Gamma rays
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13
Q

Which wave has the highest frequency?

A

Gamma rays

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14
Q

Which wave has the lowest frequency?

A

Radio waves

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15
Q

Which wave has the highest wavelength?

A

Radio waves

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16
Q

Which wave has the lowest wavelength?

A

Gamma rays

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17
Q

What are the four key properties which all EM waves have?

A
  • they are all transverse waves
  • they travel at the speed of light through a vacuum
  • they all transfer energy
  • they can all be reflected, refracted and diffracted
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18
Q

What are the detectors of radio waves?

A
  • radio and TV aerials
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19
Q

What are the detectors of microwaves?

A
  • microwave recievers
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20
Q

What are the detectors of infrared waves?

A
  • skin
  • blackened thermometer
  • special photographic film
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21
Q

What are the detectors of visible light?

A
  • the eye
  • photographic film
  • light dependant resistors
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22
Q

What are the detectors of ultraviolet?

A
  • skin
  • photographic film
  • some fluorescent chemicals
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23
Q

What are the detectors of x-rays?

A
  • photographic film
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24
Q

What are the detectors of gamma rays?

A
  • Geiger-Müller tube
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25
Q

What are the uses of radio waves?

A
  • long, medium, and short wave radio

- TV

26
Q

What are the uses of microwaves?

A
  • mobile phone and satellite communication

- cooking

27
Q

What are the uses of infrared waves?

A
  • infrared cookers and heaters
  • TV and stereo remote controls
  • night vision
28
Q

What are the uses of visible light?

A
  • seeing (duh)
  • communication in optical fibres
  • photography
29
Q

What are the uses of ultraviolet?

A
  • fluorescent tubes

- UV tanning lamps

30
Q

What are the uses of x-rays?

A
  • X-radiography to observe the internal structure of objects including human bodies
31
Q

What are the uses of gamma rays?

A
  • sterilising medical equipment and food

- radiotherapy

32
Q

What are the dangers of microwaves and how can you prevent it?

A
  • internal heating of human body tissue

- microwave ovens have shielding to prevent microwaves from reaching the user.

33
Q

What are the dangers of infrared and how can you prevent it?

A
  • skin burns

- wear insulating materials to reduce the amount of IR reaching the skin.

34
Q

What are the dangers of ultraviolet and how can you prevent it?

A
  • damage to surface cells
  • blindness
  • war suncream with UV filters and stay out of strong sunlight
35
Q

What are the dangers of gamma rays and how can you prevent it?

A

gamma rays are ionising and carry lots of energy, so can penetrate further into the body. - cell mutation
-> tissue damage or cancer

  • gamma sources kept in lead lined boxes
  • reduce exposure time when possible
36
Q

What is the law of reflection?

A

Angle of INCIDENCE = Angle of REFLECTION

37
Q

When constructing a ray diagram, the 3 important things to remember are:

A

1) The image is the same size as the object
2) The image and the object are equidistant from the mirror
3) The object is formed with diverging rays

38
Q

What is refraction?

A

When a wave enters a medium with a different density, it change speed.
If it enters the medium at an angle, one part of the wave enters before the other and the wave changes direction, or is REFRACTED.

39
Q

Describe an experiment to investigate the refraction of light

A
  • light source
  • rectangular block of glass on piece of paper

1) shine a light ray at an angle at the block. (some light is reflected but most passes through the glass and is refracted)
2) trace the incident and emergent rays onto the paper and remove the block.
3) draw on the refracted ray by joining the incident and emergent rays.

40
Q

When light passes from a less dense medium to a more dense medium, it … … and bends the normal.

A

When light passes from a less dense medium to a more dense medium, it SPEEDS UP and bends AWAY FROM the normal.

41
Q

When light passes from a more dense medium to a less dense medium, it … … and bends … the normal.

A

When light passes from a more dense medium to a less dense medium, it SLOWS DOWN and bends TOWARDS the normal.

42
Q

Why do triangular prisms disperse white light?

A
  • different wavelengths of visible light refract by different amounts so white light disperses into different colours as it enters a prism
  • the boundaries on a triangular prism aren’t parallel so the different wavelengths don’t emerge parallel and you get a rainbow effect
43
Q

What is refractive index (n)?

A

How fast light travels in a certain material

44
Q

SNELL’s LAW

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

A

n = sin i
——–
sin r

45
Q

Describe an experiment to find the refractive index of glass

A
  • light source
  • rectangular block of glass on piece of paper

1) draw around the glass block
2) shine a light ray at an angle at the block.
3) trace the incident and emergent rays onto the paper and remove the block.
4) draw on the refracted ray by joining the incident and emergent rays.
5) draw the normal in at 90° to the edge of the block at the point where the ray enters the block
6) use a protractor to measure the angles of incidence and refraction (between the normal and rays drawn)
7) calculate n using snells law

46
Q

What is the critical angle?

A

The angle of incidence beyond which rays of light passing through a denser medium to the surface of a less dense medium are no longer refracted but totally reflected.

(aka when you increase the angle of incidence to the point where the angle of refraction is 90°. There after all light is reflected internally.)

47
Q

Describe an experiment using semi-circular blocks to show total internal reflection

A
  • light source
  • semi-circular block on piece of paper

1) aim the incident light ray at the middle of the curved edge of the block so it always enters the centre of the straight side of the block at 90° to the edge.
2) alter the angle of incidence and mark the positions of the rays on the paper.
3) use a protractor to measure i and r at different angles of incidence
4) when you increase the angle of incidence so that no light is refracted, you have surpassed the critical angle.

48
Q

What is the relationship between critical angle and refractive index?

A

sin C = 1
—-
n

49
Q

What are 2 uses of total internal reflection?

A
  • optical fibres for transmitting information (endoscopes, telecommunications)
  • prismatic periscope
50
Q

To communicate any kind of information over a long distance, it needs to be converted into ……….. ……… before it is transmitted.

A

To communicate any kind of information over a long distance, it needs to be converted into ELECTRICAL SIGNALS before it is transmitted.

51
Q

What’s the difference between analogue and digital signals?

A

Analogue
- signal can take any value within a certain range (amplitude and frequency of an analogue wave can vary continuously)

Digital
- can only take two values, on/off or 1/0.

52
Q

What are the advantages of digital signals over analogue signals?

A

+ DIGITAL SIGNALS REMAIN HIGH QUALITY WHEN AMPLIFIED: All signals become weaker during transmission and need to be amplified or regenerated. When you amplify a digital signal, a clean accurate copy of the original is created, but when you amplify an analogue signal, the background electrical disturbances are amplified along with the original signal so the signal loses quality.

+ EASIER TO DESIGN AND BUILD
+ DEAL WITH EASIER TO PROCESS DATA
+ CAN CARRY MORE INFORMATION: It’s easier to transmit multiple signals simultaneously (multiplexing) if the signal is digital as signals are easier to distinguish. Also, you can round signals (quantisation) to pack the same amount of info into a smaller space as digital only has 2 values.

53
Q

What is diffraction?

A

When a wave passes through a gap or past the edge of an object, it spreads out to enable it to travel around the corners.

54
Q

If the gap is much wider than the wavelength

A

Little diffraction

55
Q

If the gap is a bit wider than the wavelength

A

Diffraction at edges

56
Q

If the gap is the same size as the wavelength

A

Maximum diffraction

57
Q

What is the frequency range for human hearing?

A

20Hz - 20,000 Hz

58
Q

Properties of sound waves

A
  • longitudinal waves
  • caused by vibrating particles
  • the denser the medium, the fasted sound travels
  • can be reflected, refracted and diffracted
59
Q

What is an oscilloscope?

A
  • an oscilloscope is a way displaying sound waves.
    Microphones can pick up sound waves travelling through air and convert them to electrical signals. If you connect a microphone to an oscilloscope, you can see the microphone signal displayed as a trace on a screen.
60
Q

The greater the amplitude, the ………………

A

The greater the amplitude, the LOUDER THE SOUND.

- the greater the amplitude of a wave, the more energy it carries. This means the sound will be louder

61
Q

The higher the frequency, the ………………

A

The higher the frequency, the HIGHER THE PITCH.
- Frequency is the number of complete waves per second. The more complete cycles per second, the higher the pitch of the sound.

62
Q

How can you use an oscilloscope to measure the speed of sound?

A
  • signal generator
  • two microphones
  • loudspeaker
  • an oscilloscope

1) Start with both microphones next to the speaker. Slowly move one away until the two waves on the oscilloscope are aligned on the display, but exactly one wavelength apart.
2) Measure the distance between the two microphones to find the wavelength (λ)
3) use the formula v = f x λ to find the speed of the sound waves through air. The frequency is what you set the simple generator to initially.

You should get about 340 m/s!

Physics (7 decks)

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