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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
Q

wavelength is…

A

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

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26
Q

What 3 wave parameters are needed to describe electromagnetic energy?

A

velocity, frequency, and wavelength

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27
Q

velocity is…

A

constant

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28
Q

With a given velocity what is the relationship of wavelength and frequency?

A

they are inversely proportional

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29
Q

What is the wave equation?

A

velocity = frequency x wavelength

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30
Q

What is the equation for electromagnetic wave?

A

c=frequency x wavelength

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31
Q

If frequency increases then wavelength

A

decreases

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32
Q

The electromagnetic spectrum includes what/

A

the entire range of electromagnetic energy

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33
Q

What are the 3 regions of the electromagnetic spectrum that are important to radiography?

A

visible light, x and gamma rays, and RF

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34
Q

What are all the portions of the electromagnetic spectrum?

A

visible light, x and gamma rays, RF, ultraviolet light, infrared light, and microwave radiation

35
Q

What modality is not a part of the electromagnetic spectrum?

A

ultrasonography

36
Q

How is light measured

A

in nanometers

37
Q

How are xrays described (units)

A

electron volt (eV)

38
Q

Photons travel in…

A

straight lines

39
Q

What is refraction?

A

when a photon is deviated from its straight path by going from one transparent medium to another

40
Q

Visible light makes up how much of the segment of the electromagnetic spectrum

A

it makes up the smallest segment

41
Q

Sunlight has 2 types of invisible light called

A

infrared and ultraviolet

42
Q

What are the characteristics of infrared light?

A

it consists of photons with wavelengths longer than those of visible light but shorter than those of microwaves.

43
Q

What is another name for infrared light?

A

radiant heat

44
Q

On the electromagnetic spectrum, where does ultraviolet light fall?

A

between visible light and ionizing radiation

45
Q

What light is responsible for sunburn?

A

ultraviolet light is responsible fore the molecular interactions that cause sunburn

46
Q

How are communication broadcasts usually identified regarding frequency of transmission?

A

radiofrequency or RF

47
Q

RF has low ____ and long ____

A

energy, wavelength

48
Q

How long RF is microwave radiation?

A

very short wavelength

49
Q

Do xrays have a higher frequency or lower frequency/wavelength?

A

higher frequency/much shorter wavelength than other types

50
Q

xrays are emitted from…

A

the electron cloud of an atom that has been stimulated artificially

51
Q

Where do gamma rays come from?

A

inside the nucleus of a radioactive atom

52
Q

If a gamma ray and xray have the same energy, can you tell them apart?

53
Q

How are each identified?

  1. visible light
  2. radiofrequency
  3. xrays
A
  1. wavelength
  2. frequency
  3. energy
54
Q

What is the difference between a photon of xradiation and a photon of light?

A

x-radiation has a much higher frequency and a shorter wavelength than visible light

55
Q

Why is the differences between x-radiation and visible light so important?

A

Because they result in differences in the way the photons interact with matter

56
Q

visible light photons tend to behave more like ____ than ____

A

waves, particles

57
Q

x-ray photons tend to behave more like ____ than ____

A

particles, waves

58
Q

Both visible light photons and x-ray photons have both types of behavior and this is known as…

A

wave-particle duality

59
Q

When do photons interact most easily with matter?

A

the the matter is approximately the same size as the photon wavelength

60
Q

x-rays interact with

A

electrons and atoms

61
Q

x-rays behave as though they were

62
Q

visible light is a ____ ____ of the electromagnetic spectrum

A

narrow portion

63
Q

On either side of the visible light spectrum are…

A

ultraviolet light and infrared light

64
Q

What kinds of light cannot be detected by the eye?

A

ultraviolet and infrared

65
Q

How can we “see” ultraviolet and infrared light?

A

photographic emulsion

66
Q

the visible light spectrum extends from …

A

from short wavelength violet radiation through green and yellow to long wavelength red radiation

67
Q

When a photon of light strikes an object, what happens?

A

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
Q

what determines what wavelengths of light are reflected?

A

the atomic and molecular structures of any object

69
Q

visible light behaves like a

70
Q

With light the shorter the photon wavelength, the what?

A

higher the photon energy

71
Q

electromagnetic energy attenuation is the reduction in intensity that results from…

A

scattering and absorption

72
Q

Describe something that is radiopaque

A

structures that absorb x-rays

73
Q

describe something that is radiolucent

A

something that transmits x-rays

74
Q

What is the formula for inverse square law?

A

I1/I2 = D2^2/D1^2

75
Q

The decrease in intensity that is inversely proportional to the square of the distance of the object from the source mathematically called…

A

the inverse square law

76
Q

The inverse square law can be applied to distances greater than…

A

7 times the longest dimension of the source

77
Q

According to the inverse square law if the distance fro the source is doubled, what happens to the intensity of the radiation?

A

it is reduced to 1/4

78
Q

According to the inverse square law if the distance is halved the intensity is…

A

increased by a factor of 4

79
Q

x-ray energy generally ranges from

A

10keV to 50 MeV

80
Q

an x-ray photon can be thought of as containing…

A

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
Q

X-rays are created with the __ __ __ and they exist with ___ or not at all.

A

speed of light; velocity

82
Q

Who got the Nobel Prize in 1918 for mathematical and physical theories that synthesized our understanding of electromagnetic radiation?

A

Max Panck, a physicist from Germany

83
Q

Photon energy is directly proportional to…

A

photon frequency

Bushong Radiology Physics (12 decks)

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