Electromagnetic Radiation Principles Flashcards
Solar energy is also known as what?
Electromagnetic radiation (EMR)
True or false: EMR is the main source of energy for remote sensing?
True
A photon (basic unit of EMR) moves as what two things?
- particles
- waves
What 3 things happen to EMR as it is transmitted between the sun and Earth?
It is:
- reflected
- transmitted
- absorbed
(dependent on the wavelength of solar radiation striking it)
Scattering vs absorption [edit this card later]
[ edit card later ]
EMR travels in waves at what speed?
The speed of light
C = 3 x 10^8 m/s
How do waves propagate through time & space?
Waves oscillate in all directions perpendicular to the direction of travel.
What is the relationship between energy of a photon (E) and wave frequency (f)?
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)
Do photons travelling at higher frequencies have more, or less energy?
More
A photon as an electromagnetic wave has what two components?
- variable electric field
- variable magnetic field
When does reflection of EMR occur versus emission of EMR?
- 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
What is ‘wavelength’?
Wavelength (λ) – distance between 2 successive crests/troughs of the wave
What is ‘frequency’?
Frequency (µ) – Number of oscillations per second
What is ‘amplitude’?
Amplitude – distance from a wave’s midpoint to its crest or trough
What is ‘period’?
Period – time it takes for two consecutive crests/troughs to pass a stationary
point
What is the relationship between wavelength and frequency?
λ α 1/µ (inverse relationship)
C = λ x µ (C = speed of light = constant)
What kind of wavelength does a high energy EM wave have?
Short wavelength
What kind of frequency does a high energy EM wave have?
High frequency
How is wavelength denoted in an equation?
λ
It looks like a little wave with a crest
How is frequency denoted in an equasion?
µ
What rays have the highest frequency, what type of wavelength do they have, and how are they used in remote sensing?
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.
What are three types of rays not used in remote sensing?
Gamma rays
X-rays
UV rays
How are most UV rays absorbed?
By ozone in the stratosphere (earth’s upper atmosphere)
What is the range of visible light?
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)
What is the range of the infared spectrum?
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)
What is the range of thermal radiation, and what does it fall under?
Infrared spectrum between 3-14 µm
How is Near-infrared & Mid-infrared is collectively referred to, and what is it sensitive to?
- “reflected infared band”
- Very sensitive to vegetation vigour
True or false: Earth emits Thermal Infared Radiation (TIR) day & night
True
What is the range of Microwave radiation, and what information is it detected to find?
1 mm < λ < 1 m
Detected to give temperature of the object that emits the microwave
Passive microwave sensors have _______ spatial resolution
Low
Do passive or active sensors have their own energy source?
Active
