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Physics P6, Waves > Properties of waves > Flashcards

Properties of waves Flashcards

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1
Q

Give 3 examples of transverse waves

A

Electromagnetic, ripples on water, s-waves (earthquake)

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2
Q

Give 3 examples of longitudinal waves

A

Sound waves, ultrasound, p-waves (earthquake)

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3
Q

What is the difference between transverse and longitudinal?

A

In transverse, oscillations are perpendicular to direction of energy transfer however in longitudinal, oscillations are parallel to direction of energy transfer.

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4
Q

Give an example that waves only transfer energy over ripples on water and not matter

A

Particles underneath floating objects (e.g. ball) do not travel because the object only bobs up and down on the water surface as the waves pass horizontally.

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5
Q

Give an example that sound waves only transfer energy in air and not matter

A

When you pluck a guitar, the sound waves don’t carry the air particles away with them to create a vacuum.

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6
Q

What is amplitude?

A

The maximum displacement of a point on a wave away from its undisturbed position.

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7
Q

What is wavelength?

A

The distance from a point on one wave to the same point on the adjacent wave.

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8
Q

What is frequency?

A

Number of waves passing a determined point each second (in Hz)

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9
Q

What is time period?

A

The time it takes for a full cycle of a wave to be completed (in seconds)

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10
Q

What is the formula linking time period and frequency?

A

T = 1/f

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11
Q

What is wave speed?

A

Speed at which energy is transferred (or the wave moves) through a medium

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12
Q

What is the wave speed equation?

A

Wave speed = frequency x wavelength

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13
Q

Describe a method to calculate speed in air with microphones?

A

1) Attach a signal generator to a speaker, with 2 microphones next to the speaker.
2) Set the signal generator to a known frequency. You will be able to see the detected wave for each mic on an oscilloscope
3) Slowly move one mic away (it’s wave will shift) and continue until the waves on the oscilloscope are aligned again
4) This is one wavelength so measure the distance between the mics and use the wave speed formula to calculate speed.

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14
Q

What is the approximate speed of sound in air?

A

330 m/s

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15
Q

What can happen when a wave hits a boundary?

A
  • Transmitted - pass through a body
  • Absorbed - taken in by a body, transferring energy to the material
  • Reflected
  • Refracted
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16
Q

What is speculation reflection?

A

This usually happens on a smooth surface where the normal is the same for each incident ray. Therefore, a clear image is produced (mirror)

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17
Q

What is diffuse reflection?

A

This happens on a rough surface. The incident ray is still equal to reflected ray however the normal is different for each producing a matt image.

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18
Q

Describe a way to investigate reflection?

A

1) Draw a straight line down a paper and line an object along it
2) shine a ray of light at the object and draw normal where it hits
3) Trace the incident and reflected ray
4) Measure the angles and repeat with different objects

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19
Q

Describe a way to investigate refraction?

A

1) Place transparent block on paper and trace around it.
2) With a ray box shine light and trace the normal where it hits the object
3) Trace incident ray and mark where it emerges on other side of block
4) Remove block and join the lines up
5) Measure the incident and refracted ray and repeat with different objects.

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20
Q

What is an electromagnetic wave?

A

Transverse waves that transfer energy from a source to an absorber

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21
Q

Why don’t electromagnetic waves need matter to travel?

A

They are made up of oscillating electric and magnetic fields?

22
Q

What speed do they all travel at through a vacuum?

A

300,000,000m/s

23
Q

What are two examples of energy transfer with electromagnetic waves?

A

1) A hot object (radiator) transfers energy by emitting infrared radiation which gets absorbed by its surroundings
2) Oscillating electrons produce radio waves in radio transmitter which carry energy to be absorbed by electrons in a receiver, causing them to oscillate.

24
Q

What are radio waves used for?

A

Radio and TV signals

25
Q

Why are long wave radio able to reach far distances?

A

They can diffract along the curved surface of the Earth

26
Q

Why can short wave radio reach shorter distances?

A

They are able to reflect off the ionsphere e.g. bluetooth

27
Q

Where do you have to stand when using TV and FM?

A

In direct sight of the transmitter

28
Q

What are microwaves used for?

A

Satellite communications and cooking

29
Q

Why can some wavelengths of microwaves be used for satellites?

A

Wavelengths that are not absorbed by water can penetrate the atmosphere and reach satellites

30
Q

Why can some wavelengths of microwaves be used for cooking?

A

Different wavelengths are absorbed by water molecules, so when they penetrate the food, they transfer energy and heat it up.

31
Q

What is infrared radiation used for?

A

Infrared cameras, cooking and electrical heaters

32
Q

Why can infrared radiation be used for cameras?

A

All objects emit infrared which can be detected by cameras and converted to an electrical signal which is displayed on screen

33
Q

Why is infrared radiation used for cooking?

A

It gets absorbed by the foods and transfers energy to it, heating and cooking it.

34
Q

How is infrared radiation used in heaters?

A

Heater contains a long piece of wire and when a current is sent through it, heats up and emits infrared radiation which transfers to thermal energy store of the surrounding?

35
Q

What are the uses of visible light?

A

To see and fibre optic communications

36
Q

How does energy (visible light) travel in fibre optics?

A

When visible light hits the walls it reflects

back into the fibre allowing it to bounce along.

37
Q

Why is visible light suited to fibre optic communications?

A

The energy will travel without being absorbed or scattered so the signal stays strong

38
Q

What are the uses of ultraviolet light?

A

Sun tanning lamps, security ink and energy efficient light bulbs

39
Q

Why is UV useful for marking valuable items in security ink?

A

When UV hits fluorescence in an ink, it will be absorbed and visible light will be emitted . This means that valuable items can be marked with invisible ink but when UV is shone at it we can see who owns it.

40
Q

Why is UV useful in energy efficient bulbs?

A

Bulbs will have glass tubes coated with fluorescent material so when the electrons emit UV (and fall to lower energy level), it hits the fluorescence and visible light is emitted.

41
Q

What are some uses of x-rays and gamma rays?

A

Medical imaging and medical treatment

42
Q

How does a radiophotograph work?

A

X-rays can pass easily through flesh but are absorbed by bone. This means on photographic paper bone remains white as it’s been exposed to the fewest x-rays and flesh turns black.

43
Q

How does radiotherapy work?

A

Gamma and x-rays are ionising radiation which means they can be used to kill cancer cells at high doses. However, there is a risk that healthy cells become ionised too so the radiation is carefully aimed directly at tumours, minimising the risk to healthy cells.

44
Q

What are some dangers of UV

A

Sunburn, skin to age prematurely, blindness, risk of skin cancer

45
Q

What are some danger of x-ray and gamma rays?

A

Ionising radiation (which knocks electrons off atoms). This can kill cells or cause mutations to DNA which can cause cancer.

46
Q

What is radiation dose?

A

Measure of risk that exposure of radiation will cause to the body

47
Q

What are some dangers of microwaves?

A

Internal organs being heated as can penetrate the skin

48
Q

Radiation dose depends on two factors. What are they?

A

1) Type of EM radiation (gamma has high energy so more dangerous)
2) How big the dose is

49
Q

How do you find frequency with a ripple tank?

A

Count no. of waves to pass a point each second and do this for 1 min. Divide by 60 to get average frequency.

50
Q

What is most likely to happen when sound waves move from a less dense material to a slightly higher one?

A

The wave will be transmitted and refract through the material as the densities are similar

51
Q

What will happen when a sound wave moves from a less dense material to an extremely dense one?

A

The wave will mostly be reflected as the difference in densities is high

52
Q

Why is a stone wall a good reflector of sound in air?

A

Stone is very dense and the greater the difference in densities between materials, the more sound energy is reflected

Physics P6, Waves (1 decks)

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