Answer:

Explanation:
Refractive Index: It is a measure to find how fast the light travels through a medium. It is ration of the speed of light in vacuum to speed of light in the medium. Speed of light is not constant and varies depending on the density of the medium.
In vacuum the speed of light is 300000 km/s and is denoted by c. When the light beam enters any medium the speed will decrease. Here it is given that the speed in plastic is v. Thus the refractive index(n) is given as:

It is a dimensionless no.
Move from higher to lower energy levels
Answer:
Plasma, Supersolid, Superfluid
Explanation:
I don't know if this is what you are looking for, but I have no idea what these even are.
Answer:
Explanation:
Suppose when bucket is half full it has a mass of 2 m rotating in a circle of radius r
When Bucket is quarter full then it has a mass of m rotating in a circle of radius r.
When an object moves in a circular path then it experiences an inward force which is given by

where v=velocity of bucket
Force in case 2 is given by

Thus
therefore force required in half bucket is more than force required in quarter bucket full.