# Surveying Questions and Answers – Remote Sensing – Interaction of EM Radiation with Earth’s Surface

This set of Tough Surveying Questions and Answers focuses on “Remote Sensing – Interaction of EM Radiation with Earth’s Surface”.

1. Which among the following is not a phenomenon in case of interaction of EM waves on earth surface?
a) Reflection
b) Absorption
c) Transmission
d) Refraction

Explanation: While the interaction of EM wave with surface of the earth, it can undergo reflection, absorption and transmission. This phenomenon depends on the texture of the surface which can make any this happen.

2. Which of the following can be changed while interaction of EM wave with a surface?
a) Intensity
b) Diffraction
c) Wave length
d) Direction

Explanation: During the interaction of EM waves with the surface of the earth, intensity, direction, wave length, polarization and phase of wave length can be changed. The change in these depends on the surface of the material it is being in contact.

3. Which of the following indicates a volume phenomenon?
a) Refraction
b) Reflection
c) Transmission
d) Diffraction

Explanation: Transmission and absorption can be indicated as volume phenomena because of the fact that these can be determined by certain internal characteristics like matter, density and condition in which it is present.

4. Determine the energy of the wave length, if the reflected, absorbed and transmitted energies were given as 56J, 24J and 7J respectively.
a) 87J
b) 78J
c) 89J
d) 17J

Explanation: The energy of the wavelength can be expressed by using the energy balance equation, which is given as Eλ = E+E+E. On substitution, we get
Eλ = 56+24+7
Eλ = 87J.

5. Find the value of reflectance if the reflected and incident energies are given as 43J and 87J.
a) 0.94
b) 0.42
c) 0.99
d) 0.49

Explanation: The reflectance can be given as the ratio of reflected energy by incident energy, which is given as E / Eλ. On substitution, we get
43 / 87 = 0.49 is the reflectance value.
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6. What will be the value of absorbance, if the absorbed and incident energies are given as 67J and 109J respectively?
a) 0.16
b) 0.61
c) 0.69
d) 0.72

Explanation: The formula of absorbance can be given as the ratio of absorbed energy by incident energy, which is represented as E / Eλ. On substitution, we get
67 /109 = 0.61 is the value of absorbance.

7. Find the transmittance, if the transmitted and incident energies are given as 156J and 987J respectively.
a) 0.51
b) 0.45
c) 0.15
d) 0.5

Explanation: The value of transmittance can be given as E / Eλ, which is the ratio of transmitted energy by incident energy. On substitution, we get
156 /987 = 0.15 is the value of transmittance.

8. What will be reflectance value if the possess an emissivity of 56.
a) 55
b) 50
c) 54
d) 52

Explanation: The relation between reflectance and emissivity can be given as ρλ = 1-ς. Here, ς is the emissivity. On substitution, we get
ρλ = 1- 56 = -55. (Negative indicates reflectance).

9. When emissivity is zero, what will be the value of reflectance?
a) One
b) Zero
c) Ten
d) Not equal to one

Explanation: When emissivity is zero, the reflectance value would be equal to one, which means the total energy incident on the object is reflected and recorded by the system. Best example for this case is snow.

10. Generally, the value of reflectance varies from __________
a) 10-20
b) 0-10
c) 0-1
d) 0-0.5

Explanation: The variance of the reflectance is generally due to the emissivity and the reflectance. The variation is under control when the emissivity is not equal to one and reflectance is equal to zero.

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