Answer:
C) Index of refraction
Explanation:
Index of refraction also known as refractive index is defined as speed of light in a vacuum divided by the speed of light in a given material.
The formula for Index of refraction is:
n = c ÷ v
where n represents Index of refraction,
c represents speed of light in a vacuum,
v represents speed of light in a given material.
The speed and direction of light changes when it moves from one medium to another. The change in direction is basically called refraction.
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In this case the rubber raft has horizontal and vertical motion.
Considering vertical motion first.
We have displacement 
, u = Initial velocity, t = time taken, a = acceleration.
In vertical motion
s = 1960 m, u = 0 m/s, a = 9.81 
So raft will take 20 seconds to reach ground.
Now considering horizontal motion of raft
u = 109 m/s, t = 20 s, a = 0
So 
So shipwreck was 2180 meter far away from the plane when the raft was dropped.
Flux=q/e0
e0=8.85*10^-12
!!! Cube has 6 sides, so flux through one side is equal to total flux/6
Ans=9.11*10^(-6)/((8.85*10(-12))*6)=(approximately)1.72*10^5Nm^2/C
