Ch. 3 Electromagnetic Energy Flashcards Preview

Bushong Radiology Physics > Ch. 3 Electromagnetic Energy > Flashcards

Flashcards in Ch. 3 Electromagnetic Energy Deck (83):
1

Photons are also known as...

electromagnetic energy

2

Where does electromagnetic energy exist?

Everywhere

3

Name some examples of electromagnetic energy

x-rays, visible light, and radiofrequencies

4

What are properties of electromagnetic energy?

frequency, wavelength, velocity, and amplitude

5

electromagnetic energy that exists over a wide range is called

an energy continuum

6

What is an atom of light called?

a photon

7

define photon

the smallest quantity of any type of electromagnetic energy

8

an x-ray photon is a ______ of electromagnetic energy

quantum

9

What properties does visible light have

electric and magnetic properties

10

how fast is the speed of light?

186,000 miles/second or
3 x 10^8 m/s

11

Why do physicists use the word field?

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

12

The electric field governs what?

the interaction of electrostatic charges

13

The magnetic field governs what?

the interaction of magnetic poles

14

How can sine waves be described?

by a mathematical formula and have many applications in physics

15

How do electrons behave in a alternating electric current?

they move back and forth sinusoidally through a conductor

16

Describe amplitude

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

17

What does a model of electromagnetic energy describe?

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

18

What are the important properties of the sine wave model?

frequency and wavelength

19

How is wavelength represented?

with the symbol lambda

20

Describe frequency

The rate of rise and fall

21

How is frequency usually identified?

cycles per second

22

What is the unit of measurement for frequency?

Hz

23

One Hz is equal to...

1 cycle per second

24

Frequency is equal to....

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

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