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Waves Flashcards

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1
Q

What are waves? What can they be described as? - Waves

A

Waves are a way in which energy may be transferred between energy stores. Can be described as oscillations about a rest position

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2
Q

What is a longitudinal wave? - Waves

A

A wave with oscillations in the same direction as the direction of energy transfer

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3
Q

What are transverse waves? - Waves

A

Transverse waves are waves with oscillations at right angles to the direction of energy transfer

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4
Q

What are mechanical waves? - Waves

A

Waves which cause oscillations in a solid, liquid or gas (must have a medium to travel through)

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5
Q

What are electromagnetic waves? - Waves

A

Waves which cause oscillation in electrical and magnetic fields

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6
Q

What are the rest position, peaks and troughs of a wave? - Waves

A

Rest position - undisturbed position of particles when they are not vibrating
Peaks - the highest point above the rest position
Trough - the lowest point below the rest position

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7
Q

What are the amplitude, wavelength and frequency of a wave? - Waves

A

Amplitude - the distance between the rest position and the peak/trough
Wavelength - distance covered by a full cycle of a wave, from peak to peak
Frequency - the number of waves passing a point each second

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8
Q

How can you calculate the time period of a wave? - Waves

A

Time period (s) = 1 / frequency (Hz)

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9
Q

How do you calculate wave speed? - Waves

A

Wave speed (m/s) = frequency (Hz) x wavelength (m)

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10
Q

How is sound heard by humans? - Waves

A

Sound causes air particles to vibrate and collide, causing them to vibrate between air particles. These particles enter an ear drum and vibrate the ear drum

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11
Q

How can the speed of sound be calculated? (Equation and method) - Waves

A

Speed (m/s) = distance (m) / time (s)
Stand an observer 400 metres away and ensure a sound is made and a hand signalled when it starts. When the sound is heard stop the clock.

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12
Q

Name 2 examples of longitudinal waves? - Waves

A

Sound waves, ultrasound waves, seismic P waves

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13
Q

Describe the structure of longitudinal waves - Waves

A

Longitudinal waves show areas of compression and rarefactions
Compressions are regions of high pressure due to particles being close together. Rarefactions are regions of low pressure due to particles being spread apart

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14
Q

Name 2 examples of transverse waves - Waves

A

Electromagnetic waves (light/radio/micro), ripples on the surface of water, seismic S-waves

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15
Q

What type of wave are electromagnetic waves? - Waves

A

Electromagnetic waves are transverse waves. Their oscillations are at right angles to the direction of wave travel

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16
Q

Describe the abilities of electromagnetic waves (where they can travel, speed, type of energy) - Waves

A

Electromagnetic waves transfer energy as radiation to an absorber
Can travel through a vacuum like space
Travel at the same speed through vacuum or air

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17
Q

What mnemonic helps remember the electromagnetic spectrum? - Waves

A

Randy Men Inject Viagra Until Xplosive Growth

Radio, Micro, Infrared, Visible Light, Ultraviolet, X-Ray, Gamma

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18
Q

Why is the visible light group unique? - Waves

A

It is the only wave in the electromagnetic spectrum which is visible to the naked eye

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19
Q

What happens to the wavelength/frequency in the electromagnetic spectrum as you go from radio -> gamma? - Waves

A

The wavelength of waves decreases, and the frequency of waves increases

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20
Q

What colour of light has the lowest frequency of all the visible light? What has the highest? - Waves

A

The colour red has the lowest frequency of all the visible light. Violet light has the highest

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21
Q

What are radio waves used for? Explain why they are useful for this - Waves

A

Radio waves used for communication, TV and radio. They are easily transmitted through air and do not damage humans if absorbed. Can be reflected to change direction

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22
Q

What are microwaves used for? Explain why they are used for this - Waves

A

Used for cooking food and satellite comms. They are easily absorbed by food molecules and increase the internal energy of food molecules which heats food. They also easily pass through the atmosphere

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23
Q

What are infrared waves used for? Explain why they are used for this - Waves

A

Used by cookers to cook food, electrical heaters. Has frequencies absorbed by some chemical bonds, and increases their internal energy, heating them.

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24
Q

What is visible light used for? Explain why it is used for this - Waves

A

Visible light is used in fibre-optic communications. It is visible which means coded light pulses can travel from a source to a receiver

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25
Q

What are ultraviolet waves used for? Explain why they are used for this - Waves

A

Used in energy efficient lamps, as these can absorb ultraviolet rays and re-emit the energy as visible light. Also used to tan skin, as it can be absorbed by humans

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26
Q

What are gamma rays used for? Explain why they are used for this - Waves

A

Gamma rays can be used to reduce cancerous growths. By firing them at a growth from different angles, focussing them at a point they do not damage individual cells, but shrink the growth. High wavelength makes them potent

27
Q

What are x-rays used for? Explain why they are used for this - Waves

A

Used for internal imaging, as they are easily absorbed by dense structures, meaning that they help identify fractures

28
Q

What is the law of reflection? - Waves

A

States that the angle of incidence = angle of reflection

If a ray hits a surface at 32° then it will be reflected at 32°

29
Q

How do you measure the angles of incidence and the angles of reflection? - Waves

A

Measure from the normal (imaginary line at 90° to the reflective surface)

30
Q

What is specular reflection? - Waves

A

Reflection from a smooth flat surface

31
Q

What is a virtual image? - Waves

A

An image made from fake rays of light

32
Q

What is a diffuse reflection? - Waves

A

If a surface is not smooth, then diffuse reflection happens. The reflected rays of light are scattered in all directions, causing a distorted object image

33
Q

Why does refraction occur in light waves? - Waves

A

Different materials have different optical densities which causes them to change speed upon meeting the dense surface

34
Q

When light passes through a substance denser than air, does it bend towards or away from the normal? - Waves

A

The light will bend towards the normal if the substance is denser than air

35
Q

For a given frequency of light, what is the relationship between wavelength and wave speed? - Waves

A

If the frequency of the light remains the same, then the wavelength is proportional to the wave speed

36
Q

What type of waves are sound waves? What does this means? - Waves

A

Sound waves are longitudinal waves, which means that the oscillations are parallel to the direction of energy transfer.

37
Q

How does the human ear process sound and allow it to be heard? - Waves

A

Sound waves enter the ear and cause the ear drum to vibrate. 3 small bones transmit these vibrations to the cochlea which makes electrical signals which pass into the brain and are interpreted as sound

38
Q

How does the frequency/amplitude of a sound wave relate to the sound heard? - Waves

A

A high frequency sound wave is high pitched, and a low frequency sound wave is low pitched
High amplitude sound waves are loud, low amplitude sound waves are quiet

39
Q

What is the range of normal human hearing? - Waves

A

20 Hz to 20,000 Hz

40
Q

What is ultrasound? - Waves

A

Ultrasound waves have a frequency higher than the upper limit of human hearing

41
Q

What can ultrasound be used for? Explain why it is used for this - Waves

A

Ultrasound can be used for breaking kidney stones or cleaning jewellery. It can do this due to its high frequency and high pitched sound

42
Q

What are seismic waves? - Waves

A

Seismic waves are shock waves that travel through the earth usually caused by an earthquake

43
Q

What are the 2 types of seismic waves? Which one is longitudinal, which one is transverse? - Waves

A

P-waves, which are longitudinal

S-waves, which are tranSverSe

44
Q

Describe whether P-waves and S-waves are slow or fast and whether they can travel through different mediums - Waves

A

P-waves: faster (PACE), travel through solids and liquids

S-waves: SLOWER, SOLIDS

45
Q

How does the study of seismic waves provide information about the structure of the earth? - Waves

A

S waves from quakes are not detected on the other side of the earth, implying that the outer core must be liquid. P waves are detected on the opposite side of the Earth. Rarefactions cause 2 zones with no P-waves. The position of these indicates a solid inner core

46
Q

What is a lens? - Waves

A

A lens is a shaped piece of transparent glass or plastic that refracts light

47
Q

What is a convex/concave lens? - Waves

A

Convex - a lens that is thicker in the middle than at the edges. Causes parallel rays to CONVERGE
Concave - a lens that is thinner in the middle than at the edges. Causes parallel rays to DIVERGE

48
Q

What is the principal focus? - Waves

A

Known as the ‘focal point’. The focus of a lens where light rays all converge or diverge to

49
Q

What is the focal length? - Waves

A

The focal length is the distance from the lens to the principal focus

50
Q

What 6 descriptions are there to describe an image formed by a lens? - Waves

A

Upright or inverted
Magnified or diminished (bigger or smaller)
Real or virtual (virtual image appears to come from behind the lens

51
Q

How do you draw a ray diagram? - Waves

A

Draw a ray from object to lens parallel to principal axis. Once through lens ray should pass through principal focus. Draw another ray passing from object through centre of lens. Where they meet is the image

52
Q

How can you calculate magnification? - Waves

A

Magnification = image height / object height

IMAGE HEIGHT AND OBJECT HEIGHT SHOULD BE GIVEN IN SAME UNITS

53
Q

What happens to a surface when it absorbs a wave? - Waves

A

The energy of a wave is transferred to the particles in a surface which increases the internal energy of the particles

54
Q

Why does grass appear green? - Waves

A

The grass absorbs the red, orange, yellow, blue, indigo and violet light, reflecting the green light which is what we see

55
Q

What happens when waves are transmitted at a boundary between 2 materials? Give an example of waves being transferred - Waves

A

The wave continues through the material and then passes through. Air, glass and water are very good at transmitting light

56
Q

When light passes through a colour filter, what happens? - Waves

A

All colours except for the wavelength of the colour of the filter is absorbed, with the colour of the filter being transmitted through the filter

57
Q

What is a perfect black body? - Waves

A

A black body is a theoretical object which would absorb all radiation which falls on it and would not reflect or transmit any radiation

58
Q

What is true of all objects that are good at absorbing energy (and therefore black bodies) - Waves

A

An object that is good at absorbing radiation is also a good emitter of radiation so a perfect black body would be a fantastic emitter of radiation

59
Q

What is considered to be a black body in space? - Waves

A

Stars are considered to be black bodies because they are very good emitters of most wavelengths of the electromagnetic, suggesting they also absorb most wavelengths

60
Q

What surfaces are the worst absorbers and emitters of visible light? - Waves

A

White and shiny surfaces are the worst absorbers as they reflect all visible light wavelengths

61
Q

What does the Earth’s temperature depend on? - Waves

A

The rate at which light and infrared radiation are absorbed by the Earth’s surface and atmosphere and the rate at which they are emitted by the Earth’s surface and atmosphere

62
Q

What happens when the Earth’s surface absorbs visible light and high frequency infrared radiation? - Waves

A

The internal energy of the Earth is absorbed and as a result the Earth’s surface gets hotter

63
Q

What can the Earth’s surface also do as well as absorb infrared and light radiation? - Waves

A

The earth can radiate low frequency infrared radiation through the atmosphere and back into space or into the atmosphere where it is absorbed by greenhouse gases

Physics (10 decks)

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