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PHYSICS IGCSE > Waves ( light and sound) > Flashcards

Waves ( light and sound) Flashcards

Topic 2 D

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1
Q

light waves are what type of waves

A

transverse waves

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2
Q

can light waves be refracted

A

yes

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3
Q

can light waves be reflected

A

yes

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4
Q

what is the law of reflection

A

angle of incidence = angle of reflection

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5
Q

properties of mirror images (4)

A
  • upright
  • same size as objects
  • laterally inverted
  • virtual ( can’t be projected on a screen)
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6
Q

frequency range for humans

A

20 - 20000 Hz

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7
Q

sound waves are what type of wave

A

longitudinal

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8
Q

reflection of a sound wave is called an

A

echo

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9
Q

sound can undergo

A

reflection and refraction

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10
Q

what waves can be reflected or refracted

A

all waves

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11
Q

reflection happens when

A

A wave hits a boundary between two media and does not pass through, but instead stays in the original medium

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12
Q

refraction happens when

A

A wave passes a boundary between two different transparent media and undergoes a change in direction

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13
Q

An incident ray has an arrow pointing towards or away from the boundary ?

A

towards

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14
Q

A reflected ray has an arrow pointing towards or away from the boundary?

A

away

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15
Q

The change in direction of the refracted ray depends on the difference in ____ between the 2 mediums

A

density

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16
Q

in refraction, From less dense to more dense (e.g air to glass), light bends to/away the normal

A

towards

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17
Q

in refraction, From more dense to less dense (e.g. glass to air), light bends away/to from the normal

A

away

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18
Q

When passing along the normal (perpendicular) the light does or doesn’t bend

A

doesn’t

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19
Q

When light passes into a denser substance the rays will slow down, so rays will bend towards/away normal

A

towards

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20
Q

The only properties that change during refraction are (2)

A

speed and wavelength

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21
Q

does frequency change during refraction

A

no

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22
Q

does light change colour when it refracts

A

no

23
Q

INVESTIGATION REFRACTION PRACTICAL

A

Place the glass block on a sheet of paper, and carefully draw around the rectangular perspex block using a pencil

Switch on the ray box and direct a beam of light at the side face of the block

Mark on the paper:

A point on the ray close to the ray box

The point where the ray enters the block

The point where the ray exits the block

A point on the exit light ray which is a distance of about 5 cm away from the block

Draw a dashed line normal (at right angles) to the outline of the block where the points are

Remove the block and join the points marked with three straight lines

Replace the block within its outline and repeat the above process for a ray striking the block at a different angle

Repeat the procedure for each shape of perspex block (prism and semi-circular)

24
Q

what is snells law

A

n = sin i
——
sin r

25
Q

what is n, i and r in snells law

A

n = the refractive index of the material

i = angle of incidence of the light (°)

r = angle of refraction of the light (°)

26
Q

what is the refractive index

A

a number that is always larger than 1 and is different for different materials

27
Q

Objects which are more optically dense have a ___ refractive index

A

higher

28
Q

Objects which are less optically dense have a ___ refractive index,

A

lower

29
Q

INVESTIGATING SNELLS LAW PRACTICAL ( aim and method)

A

AIM - To investigate the refractive index of glass, using a glass block

Place the glass block on a sheet of paper, and carefully draw around the block using a pencil

Draw a dashed line normal (at right angles) to the outline of the block

Use a protractor to measure the angles of incidence to be studied and mark these lines on the paper

Switch on the ray box and direct a beam of light at the side face of the block at the first angle to be investigated

Mark on the paper:

A point on the ray close to the ray box

The point where the ray enters the block

The point where the ray exits the block

A point on the exit light ray which is a distance of about 5 cm away from the block

Remove the block and join the points marked with three straight lines

Replace the block within its outline and repeat the above process for a rays striking the block at the next angle

30
Q

what does the refractive index measure

A

how much light will ‘bend’ when passing through a substance.

31
Q

what is the critical angle

A

angle of incidence that gives an angle of refraction of 90º

32
Q

total internal reflection happens when

A

light travels from a more dense medium to a less dense medium at an angle bigger than the critical angle

33
Q

2 conditions for total internal reflection are

A

The angle of incidence > the critical angle

The incident material is denser than the second material

34
Q

total internal reflection is used in (2)

A

optical fibres and prisms

35
Q

Total internal reflection is used to reflect light along optical fibres, meaning they can be used for (3)

A

communications

endoscopes

decorative lamps

36
Q

Prisms are used in a variety of optical instruments, including (4)

A

periscopes

binoculars

telescopes

cameras

37
Q

when light travels through a periscope, does it totally internally reflect and what does this cause

A

yes and it causes the light to reflect at right angles

38
Q

in total internal reflection, is all the light reflected ?

A

yes

39
Q

As the angle of incidence increases it will eventually surplus the ____ and lead to ____

A

critical angle

total internal reflection

40
Q

Equation between critical angle and refractive index

A

sin c = 1
—-
n

41
Q

the larger the refractive index of a material, the ___ the critical angle

A

smaller

42
Q

Light rays inside a material with a high refractive index are ___ likely to be totally internally reflected

A

more

43
Q

INVESTIGATING THE SPEED OF SOUND IN AIR ( without oscilloscope)

A

Use the trundle wheel to measure a distance of 100 m between two people

One of the people should have two wooden blocks, which they will bang together above their head to generate sound waves

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

This should be repeated several times and an average taken for the time travelled by the sound waves

Repeat this experiment for various distances, e.g. 120 m, 140 m, 160 m, 180 m

then use equation spped = distance /time to figure speed of sound

44
Q

INVESTIGATING SPEED OF SOUND USING OSCILLOSCOPE

A

Connect two microphones to an oscilloscope

Place them about 2 m apart using a tape measure to measure the distance between them

Set up the oscilloscope so that it triggers when the first microphone detects a sound, and adjust the time base so that the sound arriving at both microphones can be seen on the screen

Make a large clap using the two wooden blocks next to the first microphone

Use the oscilloscope to determine the time at which the clap reaches each microphone and the time difference between them

Repeat this experiment for several distances, e.g. 2 m, 2.5 m, 3 m, 3.5 m

speed of sound found out using equation

45
Q

An oscilloscope is a device that

A

can be used to study a rapidly changing signal, such as:

A sound wave

An alternating current

46
Q

An oscilloscope is used to display sound as

A

a waveform

47
Q

When a microphone is connected to an oscilloscope, how is the wave displayed on the screen

A

as a transverse wave

47
Q

the x-axis shows what on an oscilloscope

A

the time base

48
Q

INVESTIGATING FREQUENCY OF SOUND USING OSCILLOSCOPE PRACTICAL

A

Connect the microphone to the oscilloscope

Test the microphone displays a signal by humming

Adjust the time base of the oscilloscope until the signal fits on the screen - ensure that multiple complete waves can be seen

Strike the tuning fork on the edge of a hard surface to generate sound waves of a pure frequency

Hold the tuning fork near to the microphone and observe the sound wave on the oscilloscope screen

Freeze the image on the oscilloscope screen, or take a picture of it

Measure and record the time period of the wave signal on the screen by counting the number of divisions for one complete wave cycle

Repeat steps 4-6 for a variety of tuning forks

49
Q

If the frequency of vibration is high, the sound wave has a __ pitch

A

HIGH

50
Q

If the frequency of vibration is low, the sound wave has a ___ pitch

A

LOW

51
Q

The pitch of a sound is related to the ___ of the vibrating source of sound waves

A

Frequency

52
Q

The loudness of a sound is related to the ___ of the vibrating source of sound waves

A

amplitude

53
Q

If the sound is loud, the sound wave has a ___ amplitude

A

large

PHYSICS IGCSE (16 decks)

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