EW300 EXAM 2 PREP QUESTIONS + ANSWERS
1. What are the sections of the EO spectrum?: Ultraviolet (UV), Visible, and Infrared (IR), (which
include near, mid, far and extreme IR)
2. How are the frequencies of the EO spectrum and RADAR different?: RADAR
operates in the GHz and MHz section. EO operates in the THz section.
3. What are the advantages and disadvantages of of EO compared to RADAR?-
: Pros: passive (covert), precision imaging, VID possible
Cons: susceptible to atmospheric conditions (smoke, fog, rain), shorter range
4. What is radiant energy?: Measure of transmitted power over a duration of time [W] [J/s]
5. What is irradiance?: A measure of the power per unit area of on a surface [W/m^2]
6. What is the difference in a selective radiator and a thermal radiator?: Thermal
radiators emit across the whole EO spectrum, while selective only emit on certain wavelengths due to chemical reactions.
7. How do emissivity, absorptivity and reflexivity relate to each o ther?:
8. What is the Stefan Boltzmann law? What do you need to find this for a
greybody?: It describes the exitance of an object. For a graybody you need emissivity, becau se it accounts for
the ditterence in radiation.
9. What is point source spreading?: Point source spreading happens to most incoherent light sources,
making them shine out in a hemisphere like a flashlight, (think 1/4πR^2)
10. Do lasers have point source spreading? Why or why not?: They have minimal point
source spreading because they have coherent light, meaning laser light has same wavelength, same phase photon
emissions.
11. How do you find the divergence of a laser?: Beam divergence = range * divergence angle
(Rad)
1/5
, This gives us the diameter of the circular spot the laser produces.
12. Atmospheric absorption is dependent on what?: Wavelength!
13. The extinction coefficient accounts for what factors?: Scattering and absorption
14. What is/How do you use the Beer lambert's law?: Convert the range [R] to meters.
It accounts for transmittance
15. What is the relationship between NVG's and reflected energy?: Without reflected
light, NVG's would not work.
2/5
1. What are the sections of the EO spectrum?: Ultraviolet (UV), Visible, and Infrared (IR), (which
include near, mid, far and extreme IR)
2. How are the frequencies of the EO spectrum and RADAR different?: RADAR
operates in the GHz and MHz section. EO operates in the THz section.
3. What are the advantages and disadvantages of of EO compared to RADAR?-
: Pros: passive (covert), precision imaging, VID possible
Cons: susceptible to atmospheric conditions (smoke, fog, rain), shorter range
4. What is radiant energy?: Measure of transmitted power over a duration of time [W] [J/s]
5. What is irradiance?: A measure of the power per unit area of on a surface [W/m^2]
6. What is the difference in a selective radiator and a thermal radiator?: Thermal
radiators emit across the whole EO spectrum, while selective only emit on certain wavelengths due to chemical reactions.
7. How do emissivity, absorptivity and reflexivity relate to each o ther?:
8. What is the Stefan Boltzmann law? What do you need to find this for a
greybody?: It describes the exitance of an object. For a graybody you need emissivity, becau se it accounts for
the ditterence in radiation.
9. What is point source spreading?: Point source spreading happens to most incoherent light sources,
making them shine out in a hemisphere like a flashlight, (think 1/4πR^2)
10. Do lasers have point source spreading? Why or why not?: They have minimal point
source spreading because they have coherent light, meaning laser light has same wavelength, same phase photon
emissions.
11. How do you find the divergence of a laser?: Beam divergence = range * divergence angle
(Rad)
1/5
, This gives us the diameter of the circular spot the laser produces.
12. Atmospheric absorption is dependent on what?: Wavelength!
13. The extinction coefficient accounts for what factors?: Scattering and absorption
14. What is/How do you use the Beer lambert's law?: Convert the range [R] to meters.
It accounts for transmittance
15. What is the relationship between NVG's and reflected energy?: Without reflected
light, NVG's would not work.
2/5
