Electromagnetic Radiation Principles

Question 1

Solar energy is also known as what?

Answer 1

Electromagnetic radiation (EMR)

Question 2

True or false: EMR is the main source of energy for remote sensing?

Answer 2

True

Question 3

A photon (basic unit of EMR) moves as what two things?

Answer 3

• particles

- waves

Question 4

What 3 things happen to EMR as it is transmitted between the sun and Earth?

Answer 4

It is:

• reflected
• transmitted
• absorbed

(dependent on the wavelength of solar radiation striking it)

Question 5

Scattering vs absorption [edit this card later]

Answer 5

[ edit card later ]

Question 6

EMR travels in waves at what speed?

Answer 6

The speed of light

C = 3 x 10^8 m/s

Question 7

How do waves propagate through time & space?

Answer 7

Waves oscillate in all directions perpendicular to the direction of travel.

Question 8

What is the relationship between energy of a photon (E) and wave frequency (f)?

Answer 8

E α f
E = h x f

where,
E = energy of a photon
f = wave frequency
h = Planck’s constant (6.626 x 10-34 Joules-sec)

Question 9

Do photons travelling at higher frequencies have more, or less energy?

Answer 9

More

Question 10

A photon as an electromagnetic wave has what two components?

Answer 10

• variable electric field

- variable magnetic field

Question 11

When does reflection of EMR occur versus emission of EMR?

Answer 11

• Reflection of EMR occurs when it interacts with any material on earth
• Emission of EMR occurs when any material experiences excitation due to internal processes

Question 12

What is ‘wavelength’?

Answer 12

Wavelength (λ) – distance between 2 successive crests/troughs of the wave

Question 13

What is ‘frequency’?

Answer 13

Frequency (µ) – Number of oscillations per second

Question 14

What is ‘amplitude’?

Answer 14

Amplitude – distance from a wave’s midpoint to its crest or trough

Question 15

What is ‘period’?

Answer 15

Period – time it takes for two consecutive crests/troughs to pass a stationary
point

Question 16

What is the relationship between wavelength and frequency?

Answer 16

λ α 1/µ (inverse relationship)

C = λ x µ (C = speed of light = constant)

Question 17

What kind of wavelength does a high energy EM wave have?

Answer 17

Short wavelength

Question 18

What kind of frequency does a high energy EM wave have?

Answer 18

High frequency

Question 19

How is wavelength denoted in an equation?

Answer 19

λ

It looks like a little wave with a crest

Question 20

How is frequency denoted in an equasion?

Answer 20

µ

Question 21

What rays have the highest frequency, what type of wavelength do they have, and how are they used in remote sensing?

Answer 21

Gamma rays, they have and they have the shortest wavelength, and they are not used in remote sensing because they are completely absorbed by the upper atmosphere.

Question 22

What are three types of rays not used in remote sensing?

Answer 22

Gamma rays
X-rays
UV rays

Question 23

How are most UV rays absorbed?

Answer 23

By ozone in the stratosphere (earth’s upper atmosphere)

Question 24

What is the range of visible light?

Answer 24

0.4 µm < λ < 0.7 µm

(400 billionths of a meter < λ < 700 billionths of a meter)

3 segments:

• Blue (0.4-0.5 µm)
• Green (0.5-0.6 µm)
• Red (0.6-0.7 µm)

Question 25

What is the range of the infared spectrum?

Answer 25

From the visible portion (0.7 µm) to λ ~ 1 mm

3 segments:

• Near-infrared (0.7-1.3 µm)
• Mid-infrared (1.3-3.0 µm)
• Far-infrared (3.0-1000 µm)

Question 26

What is the range of thermal radiation, and what does it fall under?

Answer 26

Infrared spectrum between 3-14 µm

Question 27

How is Near-infrared & Mid-infrared is collectively referred to, and what is it sensitive to?

Answer 27

• “reflected infared band”

- Very sensitive to vegetation vigour

Question 28

True or false: Earth emits Thermal Infared Radiation (TIR) day & night

Answer 28

True

Question 29

What is the range of Microwave radiation, and what information is it detected to find?

Answer 29

1 mm < λ < 1 m

Detected to give temperature of the object that emits the microwave

Question 30

Passive microwave sensors have _______ spatial resolution

Answer 30

Low

Question 31

Do passive or active sensors have their own energy source?

Answer 31

Active