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PHYSICS > WAVES > Flashcards

WAVES Flashcards

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1
Q

3.2 explain the difference between longitudinal and transverse waves:

A

transverse waves:
- oscillate perpendicular to its direction of travel
- light
longitudinal waves:
- a wave which oscillates parallel to its direction o travel
- sound

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2
Q

3.3 definition of amplitude:

A

the height of the wave

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3
Q

3.3 definition of wavefront:

A

front of the wave or the same point on each waves

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4
Q

3.3 definition of frequency:

A

how many complete waves there are per second- measured in hertz

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5
Q

3.3 definition of wavelength:

A

the distance from one peak to the next

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6
Q

3.3 definition of period:

A

the time it takes (in seconds) for one complete wave to pass a point

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7
Q

3.4 do waves transfer energy?

A

yes, and information, without transferring matter

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8
Q

3.5 relationship between wave speed, frequency and wavelength:

A

wave speed= frequency x wavelength

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9
Q

3.6 relationship between frequency and time period:

A

frequency= 1/ time period

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10
Q

3.8 explain why there is a change in the observed frequency and wavelength of a wave when its source is moving relative to an observer, and that this is known as the Doppler effect:

A
  • When a car is not moving and its horn sounds, the sound waves we receive are a series of evenly spaced wavefronts.
  • If a car is moving, wavefronts of the sound are no longer evenly spaced:
  • Ahead of the car wavefronts are compressed as the car is moving in the same direction as the wavefronts. This creates a shorter wavelength and a higher frequency.
  • Behind the car wavefronts are more spread out as the car is moving away from the previous wavefronts. This creates a longer wavelength and a lower frequency.
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11
Q

3.9 can all waves be reflected and refracted?

A

yes

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12
Q

3.10 what speed do waves on the electromagnetic spectrum travel at?

A
  • same speed in free space
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13
Q

3.11 order of the electromagnetic spectrum:

A

radio, micro, infrared, visible light, ultraviolet, x-ray, gamma

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14
Q

3.11 longest and shortest wavelength on the electromagnetic spectrum:

A

longest- radio
shortest- gamma

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15
Q

3.11 lowest and highest frequency on the electromagnetic spectrum:

A

lowest- radio
highest- gamma

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16
Q

3.12 uses of radio waves?

A
  • broadcasting
  • communications
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17
Q

3.12 uses of microwaves?

A
  • cooking
  • satellite transmissions
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18
Q

3.12 uses of infared?

A
  • heaters
  • night visions equipment
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19
Q

3.12 uses of visible light?

A
  • optical fibres
  • photography
20
Q

3.12 uses of ultraviolet?

A
  • fluorescent lamps
21
Q

3.12 uses of x-rays?

A
  • observing internal structures of objects and materials, including medical applications
22
Q

3.12 uses of gamma rays?

A
  • sterilising food
  • sterilising medical equipment
23
Q

3.13 issues with microwaves:

A
  • internal heating of body tissue
24
Q

3.13 issues with infrared:

A
  • skin burns
25
Q

3.13 issues with ultraviolet:

A
  • damage to surface cells
  • blindness
26
Q

3.13 issues with gamma rays:

A
  • cancer
  • cell mutation
27
Q

3.13 how to protect yourself against the electromagnetic spectrum:

A
  • wear sun glasses, sun cream and stay in shade for UV
  • wear led clothing for Gamma
28
Q

3.14 properties of light waves:

A
  • transverse waves
  • can be reflected and refracted
29
Q

3.15 law of reflection:

A
  • angle of incidence= angle of reflection
30
Q

3.16 draw ray diagrams to illustrate reflection and refraction:

A

angle of refraction= through the block
angle of reflection= off the surface of the block

31
Q

3.17 PRACTICAL: investigate the refraction of light, using rectangular blocks, semi-circular blocks and triangular prisms:

A
  1. Set up your apparatus as shown in the diagram using a rectangular block.
  2. Shine the light ray through the glass block
  3. Use crosses to mark the path of the ray.
  4. Join up crosses with a ruler
  5. Draw on a normal where the ray enters the glass block
  6. Measure the angle of incidence and the angle of refraction and add these to your results table
  7. Comment on how the speed of the light has changed as the light moves between the mediums.
  8. Repeat this for different angles of incidence and different glass prisms.
32
Q

3.18 relationship between refractive index, angle of incidence and angle of refraction:

A

refractive index= sin i/ sin r

33
Q

3.19 investigate the refractive index of glass:

A
  1. Set up your apparatus as shown in the diagram using a rectangular block.
  2. Shine the light ray through the glass block
  3. Use crosses to mark the path of the ray.
  4. Join up crosses with a ruler
  5. Draw on a normal where the ray enters the glass block
  6. Measure the angle of incidence and the angle of refraction and add these to your results table
  7. Calculate the refractive
    index
  8. Repeat steps 2 – 7 using
    a different angle of
    incidence
  9. Find an average of your
    results.
34
Q

3.20 what does total internal reflection do when transmitting information across optical fibres?

A

used to transmit signals along optical fibres

35
Q

3.21 what is the meaning of critical angle:

A
  • The angle of incidence which produces an angle of refraction of 90 degrees (refracted ray is along the boundary of the surface).
  • When the angle of incidence is greater than the critical angle, total internal reflection occurs (all light is reflected at the boundary).
  • This effect only occurs at a boundary from a high refractive index material to a low refractive index material.
36
Q

3.22 relationship between critical angle and refractive index:

A

sin c= 1/ refractive index

37
Q

3.23 properties of sound waves:

A
  • longitudinal
  • can be reflected and refracted
38
Q

P2 3.24 what is the frequency range for human hearing?

A

20- 20 000 Hz

39
Q

P2 3.25 PRACTICAL: investigate the speed of sound in air:

A
  1. measure the distance between two people
  2. one of the people should have wooden blocks which they will bang above their head to generate sound waves
  3. the second person should have a stopwatch which they start when they see the first person banging the blocks together and stop when they hear the sound
  4. repeat this several times and an average should be taken for the time travelled by the sound waves
  5. repeat this for various distance
  6. use speed= distance/ time
40
Q

P2 3.25 what is the speed of sound in air?

A

340 m/s

41
Q

P2 3.26 understand how an oscilloscope and microphone can be used to display a sound wave

A
  • With the microphone plugged into the oscilloscope and a sound incident on the microphone, the microphone will transfer the sound into an electrical signal which the oscilloscope can display .
  • The x axis show the time base which can be adjusted for example 2ms for 1 square so time period and frequency can be calculated from this.
  • Along the y axis voltage is displayed as the wave is converted into an electrical signal this means amplitudes can be compared.
42
Q

P2 3.27 PRACTICAL: investigate the frequency of a sound wave using an oscilloscope:

A
  1. connect the microphone to the oscilloscope as shown in the image above
  2. test the microphone displays a signal by humming
  3. adjust the time base of the oscilloscope until the signal fits of the screen- ensure that multiple complete waves can be seen
  4. strike the tuing fork of the edge of a hard surface to generate sound waves of a pure frequency
  5. hold the tuning fork near to the microphone and observe the sound wave on the oscilloscope screen
  6. freeze the image on the oscilloscope screen, take a picture of it
  7. measure and record the time period of the wave signal on the screen by counting the number of divisions for one complete wave cycle
    8 . repeat steps 4-6 or a variety of tuning forks
43
Q

P2 3.28 understand how the pitch of a sound relates to the frequency of vibration of the source:

A

High frequency means high pitch. If a string vibrates with a higher frequency then the note sounds higher.

44
Q

P2 3.29 understand how the loudness of a sound relates to the amplitude of vibration of the source:

A

The greater the amplitude the louder the sound. Bigger vibrations of a sting mean more energy is being put in so more energy out as sound waves.

45
Q

what is total internal reflection?

A

all light is reflected inside of the object and is not refracted outside

46
Q

when does total internal reflection occur?

A

When the angle of incidence is greater than the critical angle, total internal reflection occurs (all light is reflected at the boundary).

PHYSICS (10 decks)

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