Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Waves 2 > Flashcards

Waves 2 Flashcards

Electromagnetic waves, Light & Lenses.

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

Use of radio waves

A

Television and radio.

They transfer energy from TV and radio transmitters to TVs and radios.

They are not transmitted by the ionosphere, instead, they are refracted and then reflected to a receiver.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why are radio waves suitable for television and radio?

A

Reflected by ionosphere (the ionized part of the Earth’s atmosphere) so can broadcast over long distances.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Use of microwaves

A

Satellite communications, cooking food.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why are radio waves suitable for satellite communications and cooking food?

A

They’re able to pass through the atmosphere to satellites.

Has a heating effect.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are electromagnetic (EM) waves?

A

Transverse waves that transfer energy from the source of the waves to an absorber. (can be an observer?)

All types of electromagnetic wave travel at the same velocity through a vacuum (space) or air - 3 x 10⁸ m/s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What do electromagnetic (EM) waves form?

A

A continuous spectrum.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How are the waves that form the electromagnetic spectrum grouped?

A

In terms of their wavelength and their frequency.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

List the EM waves from low to high frequency.

A

Radio waves
Micro waves
Infrared radiation
Visible light
Ultraviolet
X-rays
Gamma rays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

EM wave with highest frequency?

A

Gamma rays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

EM wave with lowest frequency?

A

Radio Waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

EM wave with longest wavelength?

A

Radio Waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

EM wave with shortest wavelength?

A

Gamma rays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What differentiates the EM waves?

A

Their frequencies and wavelengths which are inversely related (highest frequency = shortest wavelength, lowest frequency = longest wavelength).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why can our eyes only detect a limited range of electromagnetic waves?

A

Our eyes only detect visible light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What gives us colours?

A

Different wavelengths in the visible light region
(longest =red - hence lowest frequency, shortest = blue)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Which EM waves transfer energy from the Sun to the Earth?

A

Infrared
Visible light
UV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the wavelength of radio waves?

A

10³ m

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the wavelength of gamma rays?

A

10⁻¹² m

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Order the wavelengths of visible light from long to short (remember- the wavelength determines the colour)

A

Red
Orange
Yellow
Green
Blue
Indigo
Violet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with what?

A

wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Some effects, for example __________ are due to the difference in ________of the waves in different _________.

A

refraction
velocity
substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Students should be able to use wave front diagrams to explain refraction in terms of the change of…

A

…speed that happens when a wave travels from one medium to a different medium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

How can radio waves be produced/generated?

A

By oscillations in electrical circuits.

They can also induce an alternating current in an electrical circuit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What can happen when radio waves are absorbed?

A

When radio waves are absorbed, they may create an alternating current with the same frequency as the radio wave itself.

This means that radio waves themselves can induce oscillations in an electrical circuit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What can result in electromagnetic waves being generated or absorbed (over a wide frequency range)?

A

Changes in atoms and the nuclei of atoms.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Where do gamma rays originate?

A

From changes in the nucleus of an atom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Which EM waves can have hazardous effects on human body tissue?

A

-Ultraviolet waves
-X-rays
-Gamma rays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What does the severity of the effect of some radiation on human body tissue depend on?

A

-The type of radiation

-The size of the dose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is radiation dose?

A

A measure of the risk of harm resulting from an exposure of the body to radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is the unit for radiation dose?

A

Sieverts (Sv).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

1 sievert = how many millisieverts?

A

1000

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Students should be able to draw conclusions from given data about the what?

A

Risks and consequences of exposure to radiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Risk of X-rays and gamma rays

A

They are are ionising radiation that can cause the mutation of genes and hence cancer. (or the mutation kills cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Risk of ultraviolet waves.

A

They can can cause skin to age prematurely and increase the risk of skin cancer.

Damage to skin cells = sunburn.
Can damage the eyes leading to eye conditions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Use of Infrared radiation

A

electrical heaters, cooking food, infrared cameras.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Use of visible light

A

Fibre optic communications
To help us to see

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Use of ultraviolet waves

A

Energy efficient lamps
Sun tanning

[Security markers (invisible markings on passports, bank notes, etc. - can detect forgeries).]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Use of X-rays and gamma rays

A

Medical images and treatments.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Why are microwaves suitable for cooking food?

A

Microwaves which can be absorbed by water molecules are suitable for cooking food in microwave ovens, which transfer energy to food by microwaves. These are then absorbed by water molecules in food.

This is because when they are absorbed by water molecules in food, the energy of the waves is also absorbed.

Food molecules then vibrate faster and transfer energy to neighbouring molecules.

Energy spreads through the food via convection or conduction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Why are some microwaves suitable for satellite communications?

A

Microwaves which cannot be absorbed by water molecules are suitable for use in satellite communications.

This is because they can pass through the atmosphere without being absorbed or refracted.

They are transmitted by the ionosphere and then re-transmitted back to a receiver.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Why is infrared useful for electrical heaters and cooking food?

A

When the metals are heated to high temperatures, the metals gain lots of energy (particles vibrate faster) so emit lots of infrared radiation.

They heat food by transferring the energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Why is infrared useful for infrared cameras?

A

Infrared radiation is emitted from all objects with thermal energy however…

Animals are warmer than the surrounding environment and therefore emit more infrared radiation

Infrared cameras can detect the infrared radiation emitted by animals…

This allows them to form live images of living organisms. (shows up orange/yellow, cool= blue).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Why is visible light useful for communications using fibre optic cables?

A

Thin glass/plastic cables (the fibre optic cables) are able to transmit pulses of visible light over long distances. This is because the light waves are reflected each time they hit the inner surface.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Why is Ultraviolet useful for energy efficient lamps?

A

Fluorescent lights generate ultraviolet radiation which is absorbed by a layer of phosphorus (coating the inside of the glass bulb).

The phosphorus gains lots of energy - enough to re-emit it as visible light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Why is Ultraviolet useful for sun tanning?

A

UV chemically modifies melanin in the skin, causing the skin pigment to darken.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Why are X-rays useful for medical imaging and treatments?

A

They can be used to view the internal structure of objects- including humans:

X-rays are fired at a patient.

X-rays are absorbed by materials which are very dense, like bones, but transmitted through materials which are not very dense, like lungs and intestines.

The X-rays that pass through are detected by a detector plate to form a black area on screen.

Areas such as bones where radiation has been absorbed previously show up as white/grey for partial absorption.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Why are gamma rays useful for medical imaging and treatments?

A

Used in radiotherapy (steal from P4)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Why are gamma rays useful for sterilising medical equipment and food?

A

Gamma rays can kill microorganisms without causing damage to equipment (like boiling would= melting).

This can keep food fresh for longer and safe to eat as there are no microorganisms to break it down.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

What is fluorescence?

A

The process by which UV light is absorbed, then converted and re-emitted as visible light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Why is glass/plastic used to make fibre optic cables?

A

These materials totally reflect the visible light waves and the reflection is specular so light doesn’t scatter.

This means that the signals are less likely to be distorted during transmission.

(alt-copper wires and electricity)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Is more infrared radiation emitted by a solenoid or a normal wire?

A

A solenoid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What is visible light?

A

The spectrum of wavelengths that our eyes can detect.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

Why do we get toast and not warm bread?

A

Infrared radiation cannot penetrate the surface of objects.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Which EM waves are only harmful in high quantities?

A

-Radio
-Micro

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

How does a lens form an image?

A

By refracting light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What can happen to EM waves?

A

They can be:

-reflected off a surface
-refracted when they move from one material into another
-transmitted when they pass through a material
-absorbed by different materials

The extent to which these 4 things happen depends on the material (e.g. UV can be absorbed by skin but not Earth’s atmosphere) and the wavelengths of the EM waves.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Why can X-rays and gamma rays not reach the surface of the Earth?

A

They are absorbed by the upper atmosphere.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

Explain why it is not possible to get a suntan if you are inside a house, but it is possible to listen to the radio. (4)

A

The UV rays that cause suntans are not transmitted by the walls of houses- they are absorbed by them.

Radio waves are transmitted by the walls of houses so can be detected by a radio receiver inside the house.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

Explain why we don’t need a communication satellite to relay some radio waves.

A

They are refracted by the ionosphere and reflected back to receivers on the surface of the Earth.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What does the behaviour of EM waves in different materials depend on?

A

Their wavelength and velocity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

EM waves have different velocities in different _________…..

A

materials.

This is linked to the density of the material - denser = slower.

62
Q

Dangers of infrared radiation

A

Transfers thermal energy so too much can cause skin burns.

63
Q

Dangers of microwaves

A

Can heat the water inside our bodies causing cell damage/killing cells.

64
Q

What are the three types of radio wave?

A

-Long wave
-Short wave
-Very short wave

65
Q

What can long waves do?

A

This type of radio wave can travel long distances and diffract (bend) around the curved surface of the earth.

66
Q

What can short waves not do?

A

Diffract (bend) around the curved surface of the earth.

67
Q

What are fibre optic cables used for?

A

To transmit data really quickly over very large distances (halfway around the earth).

68
Q

Uses of gamma rays in hospitals

A

-To treat cancer
-To perform medical imaging

69
Q

What are oscilloscopes used for?

A

To display the wave frequency of an alternating current.

70
Q

Does background radiation do us harm?

A

No.

71
Q

How do lenses form images?

A

By refracting light.

(changing the direction of the waves at the boundary).

72
Q

Focal length

A

The distance from the lens to the principal focus.

73
Q

What does a convex lens do?

A

Bring parallel lines to a focus at the principal focus (behind the lens).

74
Q

What are ray diagrams used for?

A

To show the formation of images by convex and concave lenses.

75
Q

Is the image produced by a convex lens real or virtual?

A

The image can be either real or virtual.

76
Q

When would an image produced by a convex lens be virtual?

A

If an object is placed between the lens and the principal focus.

77
Q

Is the image produced by a concave lens real or virtual?

A

Always virtual.

78
Q

What makes a lens more powerful (refract more strongly)?

A

-Made of a material which refracts light less strongly

-More curved

79
Q

What would make focal length shorter?

A

A thicker lens because light is refracted more strongly so comes to a point closer to the lens.

80
Q

Where are images formed?

A

At points where all the light rays from a particular point on an object appear to come together.

81
Q

Real image

A

Light rays actually come together to form an image.

82
Q

Virtual image

A

Light rays don’t actually come together where the image appears to be.

These ‘virtual rays’ are shown using a dashed line.

83
Q

How many principal focuses are there?

A

2, one either side of a lens at the same distance away each side. They always sit on the axis (parallel line all the way through the middle of the lens, horizontally).

84
Q

Convex ‘converging’ lens

A

Focuses light using refraction.

‘Light rays come together to form an image. The image can be captured on a screen.’

85
Q

Concave ‘diverging’ lens

A

Disperses light using refraction.

‘Light rays don’t come together where the image appears to be. The image cannot be captured on a screen’.

86
Q

The more powerful the lens..

A

…the shorter the focal length as light is refracted more strongly.

87
Q

Which words do we use to describe an image?

A

-Real/virtual
-Inverted/upright
-Smaller/bigger

88
Q

Why are the images we see not inverted?

A

They are! Our brain just corrects this too quickly to notice!

89
Q

How do you draw a ray diagram for a concave lens where the object is greater than 2F?

A

-Horizontal light ray from the top of the object to the lens

-Diagonal light ray from the top of the object through the centre of the lens

-Diagonal virtual (dashed lines) and real (solid lines) light ray through the principle focus and the lens

-Smaller upright image at the intersection of the real light ray and virtual light ray

90
Q

How do you draw a ray diagram for a convex lens when the image is greater than 2F?

A

-Horizontal light ray from the top of the object to the lens

-Diagonal light ray from the top of the object through the centre of the lens

-Diagonal light ray on the right side of the lens through the principle focus

-Smaller inverted image at the intersection of the two light rays of the right of the lens

91
Q

F

A

Principal focus

92
Q

2F

A

Double the distance of the principal focus from the lens.

93
Q

How to draw ray diagrams for a convex lens with the object at less than 1F from the lens?

A

-Horizontal light ray from the top of the object to the lens

-Diagonal light ray from the top of the object through the centre of the lens

-Diagonal light ray on the right side of the lens through the principle focus

-Virtual rays traced back to where the rays would meet

-Draw object here: virtual, upright, larger.

94
Q

How can the magnification produced by a lens can be calculated?

A

using the equation:

magnification = image height ÷ object height

95
Q

What units should image height and object height both be measured in?

A

mm or cm (same units for both!)

96
Q

How are concave vs convex lenses represented in ray diagrams?

A

concave - a line with outgoing fins
convex - a line with inward turned fins

97
Q

Each colour within the visible light spectrum has its own…

A

…narrow band of wavelength and frequency.

98
Q

Which colour within the visible light spectrum has the longest wavelength?

A

Red at approximately 700nm

99
Q

Which colour within the visible light spectrum has the lowest frequency?

A

Red

100
Q

Which colour within the visible light spectrum has the highest frequency?

A

Violet

101
Q

Specular diffusion

A

Reflection from a smooth surface in a single direction.

102
Q

Diffuse reflection

A

Reflection from a rough surface which causes scattering.

103
Q

What does a magnification less than one mean?

A

The image is smaller than the object.

104
Q

How do colour filters work?

A

They absorb certain wavelengths (and colour) and transmit other wavelengths (and colour).

105
Q

What determines the colour of an opaque object?

A

The colour of an opaque object is determined by which wavelengths of light are more strongly reflected.

Wavelengths that are not reflected are absorbed.

106
Q

What colour will an object appear if all wavelengths of colour are reflected equally?

A

White

107
Q

What is black?

A

An absence of light.

108
Q

What colour will an object appear if all wavelengths of colour are absorbed?

A

Black

109
Q

Objects that transmit light are either…

A

transparent or translucent.

110
Q

Why does an opaque object have a particular colour?

A

Opaque objects do not allow for the transmission of light: wavelengths are either reflected or absorbed.

The wavelengths an object reflects determines its colour.

If all are reflected = white, and if none are reflected = black.

If red reflected = red and so on.

111
Q

What is the effect on light of passing through filters?

A

Colour filters only allow certain wavelengths of visible light to be transmitted - the rest are absorbed.

112
Q

What is the effect of viewing objects through filters?

A

Primary filters allow wavelengths only of red, green, or blue to be transmitted so only objects that reflect wavelengths of that certain colour will be seen. (others will appear black).

Colour filters not of primary colours allow wavelengths of the same colour as the filter and of the primary colours that can be added together to make that colour - through.

E.g. a yellow filter would let yellow, red, and green light through. A red filter would only transmit red light.

113
Q

The colour of an object is related to what?

A

The differential absorption, transmission and reflection of different wavelengths of light by the object.

114
Q

A transparent material…

A

Transmits nearly all of the light e.g. glass.

(Only a fraction is reflected or absorbed).

115
Q

A translucent material…

A

Only transmits some of the light e.g. frosted glass.

The proportion of light transmitted determines how well we can see through.

116
Q

All bodies (objects), no matter what ___________, emit and absorb ________ _________. The hotter the body, the more ________ _________ it radiates in a given ____.

A

temperature
infrared radiation
infrared radiation
time

117
Q

What is a perfect black body?

A

An object that absorbs all of the radiation incident on it.

A black body does not reflect or transmit any radiation.

Since a good absorber is also a good emitter, a perfect black body would be the best possible emitter.

118
Q

What does the intensity of any emission (of infrared radiation) depend on?

A

The temperature of the body (object).

119
Q

What does the wavelength distribution of any emission (of infrared radiation) depend on?

A

The temperature of the body (object).

e.g. the sun (surface 5700°C) which is much hotter than a cup of tea (90°C) will emit visible light and ultraviolet which have a shorter wavelength than infrared.

120
Q

Thermal equilibrium

A

When thermal radiation is absorbed and emitted from an object at the same rate.

A body at constant temperature is absorbing radiation at the same rate as it is emitting radiation.

121
Q

When does the temperature of a body (object) increase?

A

When the body absorbs radiation faster than it emits radiation.

122
Q

Body =

A

Object.

123
Q

Factors affecting the temperature of the Earth?

A

-The rates of absorption and emission of radiation

-Reflection of radiation into space.

124
Q

When does the temperature of a body (object) decrease?

A

When the body emits radiation faster than it absorbs radiation.

125
Q

Give an everyday example to illustrate the balance between incoming radiation absorbed and radiation emitted.

A

The water inside a kettle cools down because it emits infrared radiation faster than it absorbs it.

126
Q

What is intensity (P6-waves)?

A

The energy emitted per square metre per second/ the power emitted per square metre.

127
Q

As an object gets hotter, the _________ increases and the __________ ____ ___________ __ ___ _______ _________ decreases.

A

intensity

wavelength that corresponds to the maximum intensity (peak wavelength)

128
Q

Order in terms of hotness: red, white, blue

A

Blue
Red
White (hence a safety flame’s colour)

129
Q

On an intensity wavelength graph, what does the area under the line tell us?

A

How intense/total power - larger area=bigger

130
Q

Violet light wavelength

A

410nm so refracted more than other colours

131
Q

How can we split up white light?

A

Using a prism.

The white light ray is refracted into a spectrum of colours (dispersion).

132
Q

What do primary colours (R,G,B)add to make?

A

White

133
Q

What are the primary colours (visible light)

A

Red
Blue
Green

134
Q

What are the secondary colours (visible light)?

A

Yellow
Cyan
Magenta
White

135
Q

How to make yellow light?

A

Red and Green

136
Q

How to make cyan light?

A

Green and Blue

137
Q

How to make magenta light?

A

Red and Blue

138
Q

How might we investigate the transmission of primary and secondary colours?

A

Using a light box and coloured filters.

139
Q

How many wavelengths make up yellow light (secondary)

A

3
(yellow, green, red)

140
Q

Wavelength of microwaves

A

10⁻²m

141
Q

Wavelength of infrared

A

10⁻⁵m

142
Q

Wavelength of UV

A

10⁻⁸m

143
Q

Wavelength of an X-ray

A

10⁻¹⁰m

144
Q

How does temperature affect the wavelength that is radiated most intensely (the peak wavelength)?

A

The peak wavelength decreases as temperature increases.

145
Q

Object A emits s a peak wavelength of light of 600nm, and object B emits a peak wavelength of light of 750nm.

Which of the 2 objects is hotter? Explain your answer.

A

Object A is hotter.

The hotter the object, the shorter the peak wavelength.

146
Q

How does temperature affect the intensity of all wavelengths emitted by a black body?

A

The intensity of all wavelengths increases wit temperature.

147
Q

A hotter, bigger, or brighter object gives out more what?

A

Energy. (in the form of infrared radiation)

148
Q

(HT only) Students should be able to use information, or draw/interpret diagrams to show how radiation affects the temperature of the Earth’s surface and atmosphere.

A

MHMMM?

149
Q

Blue light wavelength?

A

≈500nm

150
Q

Green light wavelength?

A

≈550nm

151
Q

Yellow light wavelength?

A

≈570nm

152
Q

Orange light wavelength?

A

≈600nm

Physics (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions