Answer:
The critical angle for light is 41.81 degrees.
Explanation:
We have, light is propagating from a material with index of refraction of 1.50 to a material with index of refraction of 1. It is required to find the critical angle for light. It is angle for which the angle of refraction is equal to 90 degrees. It is given by :

So, the critical angle for light is 41.81 degrees.
Calculate it by mass and volume.
R = ρl/A
From the equation above R = Resistance, l = length, A = Cross Sectional Area of wire.
From the equation, it can be seen that R would increase if the wire's area is reduced.
If the area of the wire is reduced, means the same thing as:
<span>A. decreasing the wire’s thickness</span>