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GCSE Physics > 5) Light & The Electromagnetic Spectrum > Flashcards

5) Light & The Electromagnetic Spectrum Flashcards

(95 cards)

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1
Q

What wave type are all electromagnetic waves?

A

Transverse

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2
Q

What speed do all EM waves travel at in a vacuum?

A

The same speed

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3
Q

What are the 7 types of EM wave?

A 
Gamma
X-ray
Ultravoilet
Visible
Infrared
Microwave
Radio waves
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4
Q

Which EM wave carries the most energy?

A

Gamma rays

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5
Q

How do gamma rays’ wavelength and frequency compare to the other EM waves?

A

Shortest wavelength

Highest frequency

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6
Q

How do radio waves’ wavelength and frequency compare to the other EM waves?

A

Longest wavelength

Lowest frequency

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7
Q

What happens to the freqquency as wavelength increases?

A

Frequency decreases

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8
Q

What are uses of gamam rays?

A

Medical imaging and therapy
Astronomy
Sterilisation
Food preservation

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9
Q

What are risks of gamma rays?

A

Extremely penetrating and damaging to living tissues and cells

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10
Q

What do we use gamma rays to destroy?

A

Bacteria

Tumours

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11
Q

What are uses of x-rays?

A

Medical and industrial imaging
Treating cancer
Security purposes

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12
Q

Why are x-rays used to scan the body?

A

X-rays penetrate soft materials (body tissue)

Bones are dense and absorb x-rays

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13
Q

What are risks of x-rays?

A

Highly ionising (can damage body cells)

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14
Q

How can you shield yourself from x-rays?

A

Place metals or lead between yourself and the x-rays

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15
Q

What are risks of ultraviolet light?

A

Skin burns
Skin cancer
Cataract formations in the eye

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16
Q

What are uses of ultraviolet light?

A 
Medical and forensic photography
Air purification
Water disinfection
Medical therapy
Detecting fake notes
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17
Q

What do UV photons do to atoms?

A

They give energy to atoms causing them to release visible light

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18
Q

What are risks of infra-red radiation?

A

Serious skin burns if emitted from high intensity sources

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19
Q

What do infra-red lights do to food?

A

Excite the particles causing an increase in temperature

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20
Q

What are uses of infra-red light?

A

TV controls
Security purposes
Body heat detectors

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21
Q

What are uses of microwaves?

A

Satellite communications
Phone signals
Heating food and drink

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22
Q

Why are microwave used for satellite communications?

A

They have a high enough frequency to penetrate the Earth’s atmosphere
Travel in straight lines

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23
Q

What are risks of microwaves?

A

Humans are made up of water so exposure could be harmful

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24
Q

How do we use safety with microwaves?

A

Using protective shielding

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25
What molecules can microwaves transfer energy to?
Water molecules
26
What are risks of radio waves?
High intensities can cause internal heating of tissue
27
What are uses of radio waves?
Radio and TV communications
28
What does radio waves' long wavelength mean?
They can be transmitted around the Earth's surface and buildings without interference
29
How can electromagnetic waves be produced?
Electrical circuits | Changes in atoms
30
What do changes in atoms produce?
Radiation of lots of different frequencies
31
How are EM waves produced in electrical circuits?
Oscillations can produce radio waves
32
What happens when radio waves are absorbed?
They can create an AC current with the same frequency as the radio wave itself This means radio waves can lead to oscillations in an electrical circuit
33
How are EM waves produced in changes in atoms?
Changes in the nuclei can result in EM waves being generated or absorbed over a wide frequency range
34
Where do gamma rays originate from?
Changes in the nucelus of an atom
35
What are the 7 colours of the visible light spectrum?
``` Red Orange Yellow Green Blue Indigo Violet ```
36
Why can we use visible light in optical fibres?
It can be totally internally reflected
37
What are uses of visible light?
We use visible light to see the world | Fibre optics
38
What determines the opacity of an object?
Whether light is absorbed, reflected or transmitted
39
What are the 3 opacities?
Opaque Translucent Transparent
40
What happens to light to make objects translucent?
Light is transmitted but rays are scattered
41
What happens to light to make objects opaque?
Light is either reflected or absorbed
42
What happens to light to make objects transparent?
Light is transmitted without scattering rays
43
Which colour has the lowest frequency and longest wavelength?
Red
44
Which colour has the highest frequency and shortest wavelength?
Violet
45
What are the two ways light can be reflected?
Diffuse | Specular
46
What is diffuse reflection?
When light is scattered by a rough surface
47
What is specular reflection?
Light is reflected in a single direction by a smooth surface
48
What is the colour of an opaque object when all of the wavelengths are reflected equally?
White
49
What is the colour of an opaque object when all of the wavelengths are absorbed?
Black
50
What happens to wavelengths when an object has a particular colour?
It reflects all of the particular wavelength (colour) | Absorbs all other wavelengths
51
What do colour filters do?
Absorb certain wavelengths and transmit other wavelengths
52
What is internal reflection?
When light speeds up when entering a less optically dense medium Some light is refracted and some light is reflected
53
What happens if the angle of incidence is the same as the critical angle?
Light will travel along the boundary of the 2 mediums
54
What is total internal reflection?
If the angle of incidence exceeds the critical angle all of the light will be reflected
55
How does a lens form an image?
By refracting light
56
What are the main types of lens?
Converging (convex) | Diverging (concave)
57
How does the power of a lens increase?
When the difference between the middle thickness and edge thickness increases
58
How does a convex lens' power increase?
Thicker middle comapred to edges
59
How does a converge lens' power increase?
Thinner middle compared to edges
60
What is the equation for power of a lens?
``` P = 1 / f Power = 1 / focal length ```
61
How does the focal length size affect the power?
Larger focal length = lower power
62
What is the focal length?
The distance between the lens and the principle focus
63
How does a lens form an image?
By refracting light
64
What does a convex lens look like?
Wider in middle than edges
65
Where is the principal focus of a convex lens?
Where all rays hitting the lens parallel to the axis meet
66
What does a converge lens look like?
Wider edges than middle
67
What happens when parallel light rays enter a concave lens?
They disperse
68
Where is the principal focus of a concave lens?
Tracing back along the path of the dspersed rays, they will come from the principal focus behind the lens
69
What type of images can convex lenses produce?
Real or virtual
70
Whattype of images can concave lenses produce
Only virtual
71
What is the equation to calculate the magnification a lens produces?
Magnification = image height / object height
72
What is the unit for magnification?
It is a ratio | No units
73
What can we not project onto a screen?
Virtual images
74
Where does a virtual image appear?
On the same side of the lens to the object
75
Where does a real image appear?
On the other side of the lens to the object
76
How do you draw ray diagrams?
1) Draw the principal axis (horizontal line straight through middle of lens) 2) Use correct lens symbols 3) Mark princiapl focus on either side of the lens, draw on dot on principal axis and label it F 4) Mark position of the object as an arrow standing on principal axis 5) Draw light rays
77
What is the symbol for convex lenses in ray diagrams?
Double headed arrow
78
What is the symbol for concave lenses in ray diagrams?
Inverted double headed arrow
79
How do you draw a convex lens ray diagram?
1) Draw line from top of object to lens 2) From point on lens draw second line through principal focus on other lens side 3) Draw third line from top of object straight through mid of lens 4) If lines meet on other lens side this forms a real image 5) Draw image as a vertical arrow connecting the point lines meet to principal axis 6) If lines do not meet this forms a virtual image
80
What do all objects emit?
Radiation
81
Where will an object always transmit heat to?
Hotter area to colder area
82
When is the rate of temperature emission higher?
When an object's internal temperature is higher than the environment's temperature
83
What does a body at constant temperature do with radiation?
Absorbs radiation at the same rate it emits radiation
84
What is the process of the greenhouse effect?
1) Sun emits short wavelength infrared radiation 2) Earth absorbs some radiation but long wavelength is reflected 3) Greenhouse gases can't absorb frequency emitted by sun but can absorb longer wavelength radiation 4) Gases re-radiate energy towards Earth 5) Earth's temperature increases
85
What length wavelengths does the sun emit?
Short wavelength infrared radiation
86
What length wavelength does the Earth reflect?
Long wavelength radiation
87
What are 3 types of greenhouse gases?
Methane Carbon dioxide Water vapour
88
What does the temperature of a body (object) depend on?
Rate of absorbtion and rate of emission of radiation
89
What factors affect the rate of emission and absorbtion?
Surface area External temperature Internal temperature
90
How much solar energy per square metre falls on Earth?
340 Watts
91
What percentage of solar energy is reflcted to space?
29%
92
What percentage fo solar energy is absorbed in the atmosphere?
23%
93
What percentage of solar energy is absorbed at the surface?
48%
94
Why can infra-red radiation travel through space?
It does not need a medium
95
What can be said about the amount of energy absorbed and emitted by the sun?
It is in balance

GCSE Physics (14 decks)

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