Answer:
C ) 1.53
Explanation:
The critical angle of a material is given by the formula

where
c is the critical angle
n is the refractive index
This formula is valid if the second medium is air (which is the case of the problem).
In this problem, we know the critical angle:

Therefore we can rearrange the equation to find the refractive index:

The electric potential energy of the electron depends on the potential difference applied between the two ends of the cable. Indeed, the electric potential energy of a charge is given by

where q is the magnitude of the charge, while

is the potential difference applied. So, U depends on

.
When you rub inflated balloon with your hair or your kitten's fur, charge is induced on all over the balloon's surface. This is called "charging by friction" because you developed charges by rubbing to bodies with each other. It will also stick on your wall you can check it out. This is because of "unlike charges attract each other". Rubbed balloon and wall possessed unlike charges which made them stick together.
The power delivered is equal to the product between the voltage V and the current I:

This power is delivered for a total time of

, so the total energy delivered to the battery is