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Bushong Radiology Physics > Ch. 3 Electromagnetic Energy > Flashcards

Ch. 3 Electromagnetic Energy Flashcards

1
Q

Photons are also known as…

A

electromagnetic energy

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2
Q

Where does electromagnetic energy exist?

A

Everywhere

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3
Q

Name some examples of electromagnetic energy

A

x-rays, visible light, and radiofrequencies

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4
Q

What are properties of electromagnetic energy?

A

frequency, wavelength, velocity, and amplitude

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5
Q

electromagnetic energy that exists over a wide range is called

A

an energy continuum

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6
Q

What is an atom of light called?

A

a photon

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7
Q

define photon

A

the smallest quantity of any type of electromagnetic energy

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8
Q

an x-ray photon is a ______ of electromagnetic energy

A

quantum

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9
Q

What properties does visible light have

A

electric and magnetic properties

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10
Q

how fast is the speed of light?

A

186,000 miles/second or

3 x 10^8 m/s

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11
Q

Why do physicists use the word field?

A

to describe interactions among different energies, forces, or masses that can otherwise be described only mathematically

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12
Q

The electric field governs what?

A

the interaction of electrostatic charges

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13
Q

The magnetic field governs what?

A

the interaction of magnetic poles

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14
Q

How can sine waves be described?

A

by a mathematical formula and have many applications in physics

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15
Q

How do electrons behave in a alternating electric current?

A

they move back and forth sinusoidally through a conductor

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16
Q

Describe amplitude

A

it is one half the range from crest to valley over which the sine wave varies

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17
Q

What does a model of electromagnetic energy describe?

A

variations in the electric and magnetic field as the photon travels with velocity

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18
Q

What are the important properties of the sine wave model?

A

frequency and wavelength

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19
Q

How is wavelength represented?

A

with the symbol lambda

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20
Q

Describe frequency

A

The rate of rise and fall

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21
Q

How is frequency usually identified?

A

cycles per second

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22
Q

What is the unit of measurement for frequency?

A

Hz

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23
Q

One Hz is equal to…

A

1 cycle per second

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24
Q

Frequency is equal to….

A

the number of crests or the number of valleys that pass the point of an observer per unit of time

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25
wavelength is...
the distance from one crest to another, from one valley to another, or from any point on the sine wave to the next corresponding point
26
What 3 wave parameters are needed to describe electromagnetic energy?
velocity, frequency, and wavelength
27
velocity is...
constant
28
With a given velocity what is the relationship of wavelength and frequency?
they are inversely proportional
29
What is the wave equation?
velocity = frequency x wavelength
30
What is the equation for electromagnetic wave?
c=frequency x wavelength
31
If frequency increases then wavelength
decreases
32
The electromagnetic spectrum includes what/
the entire range of electromagnetic energy
33
What are the 3 regions of the electromagnetic spectrum that are important to radiography?
visible light, x and gamma rays, and RF
34
What are all the portions of the electromagnetic spectrum?
visible light, x and gamma rays, RF, ultraviolet light, infrared light, and microwave radiation
35
What modality is not a part of the electromagnetic spectrum?
ultrasonography
36
How is light measured
in nanometers
37
How are xrays described (units)
electron volt (eV)
38
Photons travel in...
straight lines
39
What is refraction?
when a photon is deviated from its straight path by going from one transparent medium to another
40
Visible light makes up how much of the segment of the electromagnetic spectrum
it makes up the smallest segment
41
Sunlight has 2 types of invisible light called
infrared and ultraviolet
42
What are the characteristics of infrared light?
it consists of photons with wavelengths longer than those of visible light but shorter than those of microwaves.
43
What is another name for infrared light?
radiant heat
44
On the electromagnetic spectrum, where does ultraviolet light fall?
between visible light and ionizing radiation
45
What light is responsible for sunburn?
ultraviolet light is responsible fore the molecular interactions that cause sunburn
46
How are communication broadcasts usually identified regarding frequency of transmission?
radiofrequency or RF
47
RF has low ____ and long ____
energy, wavelength
48
How long RF is microwave radiation?
very short wavelength
49
Do xrays have a higher frequency or lower frequency/wavelength?
higher frequency/much shorter wavelength than other types
50
xrays are emitted from...
the electron cloud of an atom that has been stimulated artificially
51
Where do gamma rays come from?
inside the nucleus of a radioactive atom
52
If a gamma ray and xray have the same energy, can you tell them apart?
no
53
How are each identified? 1. visible light 2. radiofrequency 3. xrays
1. wavelength 2. frequency 3. energy
54
What is the difference between a photon of xradiation and a photon of light?
x-radiation has a much higher frequency and a shorter wavelength than visible light
55
Why is the differences between x-radiation and visible light so important?
Because they result in differences in the way the photons interact with matter
56
visible light photons tend to behave more like ____ than ____
waves, particles
57
x-ray photons tend to behave more like ____ than ____
particles, waves
58
Both visible light photons and x-ray photons have both types of behavior and this is known as...
wave-particle duality
59
When do photons interact most easily with matter?
the the matter is approximately the same size as the photon wavelength
60
x-rays interact with
electrons and atoms
61
x-rays behave as though they were
particles
62
visible light is a ____ ____ of the electromagnetic spectrum
narrow portion
63
On either side of the visible light spectrum are...
ultraviolet light and infrared light
64
What kinds of light cannot be detected by the eye?
ultraviolet and infrared
65
How can we "see" ultraviolet and infrared light?
photographic emulsion
66
the visible light spectrum extends from ...
from short wavelength violet radiation through green and yellow to long wavelength red radiation
67
When a photon of light strikes an object, what happens?
it sets the object's molecules into vibration. The orbital electrons of some atoms of certain molecules are excited to an energy level that is higher than normal. The energy is immediately re-emitted as another photon of light and it is reflected
68
what determines what wavelengths of light are reflected?
the atomic and molecular structures of any object
69
visible light behaves like a
wave
70
With light the shorter the photon wavelength, the what?
higher the photon energy
71
electromagnetic energy attenuation is the reduction in intensity that results from...
scattering and absorption
72
Describe something that is radiopaque
structures that absorb x-rays
73
describe something that is radiolucent
something that transmits x-rays
74
What is the formula for inverse square law?
I1/I2 = D2^2/D1^2
75
The decrease in intensity that is inversely proportional to the square of the distance of the object from the source mathematically called...
the inverse square law
76
The inverse square law can be applied to distances greater than...
7 times the longest dimension of the source
77
According to the inverse square law if the distance fro the source is doubled, what happens to the intensity of the radiation?
it is reduced to 1/4
78
According to the inverse square law if the distance is halved the intensity is...
increased by a factor of 4
79
x-ray energy generally ranges from
10keV to 50 MeV
80
an x-ray photon can be thought of as containing...
an electric field and magnetic field that vary sinusoidally at right angles to each other with a beginning and end that have diminishing amplitude.
81
X-rays are created with the __ __ __ and they exist with ___ or not at all.
speed of light; velocity
82
Who got the Nobel Prize in 1918 for mathematical and physical theories that synthesized our understanding of electromagnetic radiation?
Max Panck, a physicist from Germany
83
Photon energy is directly proportional to...
photon frequency

Bushong Radiology Physics (12 decks)

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