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Physics > 3 Waves > Flashcards

3 Waves Flashcards

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1
Q

what is hertz measuring

A

the frequency of something

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2
Q

what is the frequency of a wave

A

the amount of cycles per second

the pitch

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3
Q

longitudinal waves

A

the waves oscillate in the parallel (same direction) to the direction they travel in

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4
Q

transverse waves

A

the waves oscillate perpendicular (at right angles) to the direction they travel in

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5
Q

examples of longitudinal waves

A

sound waves
seismic p-waves
spring/slinkie

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6
Q

examples of transverse waves

A

electromagnetic waves
ripples in the sea
mexican wave
seismic s-waves
rope

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7
Q

what is the amplitude of a wave

A

The distance from the undisturbed position to the peak or trough of a wave

the volume

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8
Q

what is the wavefront of a wave

A

the wavefront is a way of drawing a wave from above (all of the waves are drawn in the same phase, eg all troughs)

each line represents one wave and if they are close together that shows a high frequency

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9
Q

what is the wavelength of a wave

A

The distance from one point on the wave to the same point on the next wave

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10
Q

what is the period of a wave

A

the time it takes for one wavelength to happen

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11
Q

what do waves transfer

A

transfer energy and information, without transferring matter

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12
Q

what is the formula with wavelength, frequency, wave speed

A

wave speed = frequency x wavelength
v=fλ

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13
Q

what is the formula with frequency and time period

A

frequency = 1 / time period
f=1/T

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14
Q

what is the doppler effect

A

the change in wavelength and frequency of a wave emitted by a moveing source

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15
Q

why does the doppler effect change the frequency of a wave

A

When the source of the wave is moving towards the observer, each successive wave cycle is emitted from a position closer to the observer than the previous cycle. As a result, the time between the arrival of each wave at the observer is reduced, which effectively increases the frequency of the wave as observed by the observer2.

Conversely, if the source of the wave is moving away from the observer, each wave cycle is emitted from a position farther from the observer than the previous cycle. This increases the time between the arrival of each wave at the observer, effectively reducing the observed frequency

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16
Q

why does the doppler effect change the wavelength of a wave

A

When the source of the wave is moving towards the observer, each successive wave cycle is emitted from a position closer to the observer than the previous cycle1. This causes the wavefronts to “bunch up”, effectively shortening the wavelength as observed by the observer3. This is why waves appear “squeezed” or “compressed” when the source is moving towards the observer4.

Conversely, if the source of the wave is moving away from the observer, each wave cycle is emitted from a position farther from the observer than the previous cycle1. This causes the wavefronts to spread out, effectively lengthening the wavelength as observed by the observer3. This is why waves appear “stretched out” when the source is moving away from the observer

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17
Q

can all waves be reflected or refracted

A

yes in the right circumstances

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18
Q

what type of wave is light waves

A

transverse

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19
Q

can light waves be reflected or refracted

A

yes

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20
Q

what is the law of reflection

A

The law of reflection states that the angle of incidence (the angle at which the wave hits the surface) equals the angle of reflection (the angle at which the wave bounces off the surface).

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21
Q

what is reflection

A

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

where angle i = r

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22
Q

what is the formula with refractive index, angle of incidence, angle of refraction

A

refractive index = sin(angle of incidence) / sin(angle of refraction)
n = sin(i) / sin(r)

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23
Q

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

A

Place the 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

practical: investigate the refractive index of glass using a glass block

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

measure the angle of incidence and angle of refraction and then use n = sin(i) / sin(r)

25
Q

what is total internal reflection

A

Total Internal Reflection (TIR) is where waves arriving at the boundary from one medium to another (e.g., from water to air) are not refracted into the second (“external”) medium, but completely reflected back into the first (“internal”) medium

26
Q

when does total internal reflection happen

A

The angle of incidence is greater than the critical angle and the incident material is denser than the second material

27
Q

what are the conditions needed for total internal reflection

A

The angle of incidence > the critical angle
higher refractive index than air
when a ray tries to go from a denser to a less dense material

28
Q

how is total internal reflection used in optical fibres

A

they are made of glass or plastic with in outer cladding which has a lower refractive index than the glass
which means that the light will always hit a boundary at a higher value than the critical angle

the light waves are totally internal reflected down whole wire meaning all of the wave reaches the other end which allows all of the information to to be passed through the fibre without any being lost

29
Q

what is the critical angle

A

the angle where the light is refracted along the boundary of the surface

As the angle of incidence is increased, the angle of refraction also increases until it gets closer to 90°
When the angle of refraction is exactly 90° the light is refracted along the boundary
At this point, the angle of incidence is known as the critical angle c

30
Q

what is the formula with critical angle and refractive index

A

sin(critical angle) = 1 / refractive index
sin(c)=1/n

31
Q

what type of wave is a sound wave

A

longitudinal waves

32
Q

can sound waves be reflected and refracted

A

yes

33
Q

what is the frequency range of human hearing

A

20Hz - 20,000Hz

34
Q

practical: investigate the speed of sound in air

A

have 2 people stand 300 meters (measured with a trundle wheel) away from each other
one has a pair of cymbals and the other has a stopwatch
the person with the cymbals hits them together and then the stopwatch person starts the timer when they see the cymbals hit and stops it when they hear the sound.
record the time
repeat this 3 times and work out average time
s=d/t
increase distance and repeat

35
Q

how can a oscilloscope and microphone be used to display a sound wave

A

Microphone Connection: A microphone is connected to an oscilloscope. The microphone captures sound waves and converts them into electrical signals
Signal Conversion: The oscilloscope takes these electrical signals and converts them into a visual representation, displaying them as transverse waves on its screen

36
Q

practical: investigate the frequency of a sound wave using an oscilloscope

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 the number of squares for one complete cycle

multiply the number of squares by the time base to find the time period

frequency = 1/T

37
Q

how does the pitch of a sound relate to the frequency of vibration

A

the higher the pitch of a sound, the higher frequency the wave has

38
Q

how does the volume of a sound relate to the amplitude of vibration

A

the higher the amplitude of a wave, the louder the sound is

39
Q

what happens to a wave if it enters a more dense material at an angle

A

it will bend towards the normal

40
Q

what happens to a wave if it enters a less dense material at an angle

A

it will bend away from the normal

41
Q

what is light part of

A

a continuous electromagnetic spectrum that includes radio, microwave, infrared, visible, ultraviolet, x-ray and gamma ray radiations, and that all these waves travel at the same speed in free space

42
Q

order of the EM spectrum, in terms of decreasing wavelength and increasing frequency

A

low energy, long wavelength, low frequency
radio
microwaves
infared
visible
ultraviolet
xray
gamma
high energy, short wavelength, high frequency

43
Q

order of colours of the visible spectrum

A

longest wavelength, low frequency
red
orange
yellow
green
blue
indigo
violet
short wavelength, high frequency

44
Q

uses of radiowaves

A

broadcasting and communications

45
Q

uses of microwaves

A

cooking and satellite transmissions

46
Q

uses of infrared

A

heating and night vision equipment

47
Q

uses of visible light

A

photography + optical fibres

48
Q

uses of ultraviolet

A

fluorescent lamps + tanning beds

49
Q

uses of xrays

A

observing internal structure of objects and materials including for medical uses

50
Q

uses of gamma rays

A

sterilising food and medical equipment

51
Q

effects of excessive exposure of microwaves

A

internal heating of body tissue -> prevented with metal walls and metal grid in glass door

52
Q

effects of excessive exposure of infrared

A

surface skin cell burns -> prevented with protective clothing

53
Q

effects of excessive exposure of ultraviolet

A

damage to surface skin cells and blindness -> prevented with sunglasses for eyes and suncream for skin

54
Q

effects of excessive exposure of gamma rays

A

cancer + mutation -> prevented with minimal exposure and lead clothing

55
Q

effects of excessive exposure of xrays

A

cancer + mutation -> prevented with minimal exposure and lead clothing

56
Q

effects of excessive visible light wave exposure

A

vision impairments -> don’t look into the sun and wear sunglasses

57
Q

what speed do waves travel at in a vacuum

A

all travel at speed of light

Physics (9 decks)

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