<span>A very rare type of lightning that appears as a reddish-colored sphere is called </span>A + Ball Lightening
When light changes the medium it travels through it also changes speed. The speed in medium is given by formula:

Rearranging formual gives:

From this formula we can make conclusion that index of refraction is inversely proportional to speed of light in medium. This means that greater speed gives smaller index of refraction.
What are the answer choices, if there are any?
Answer:
Explanation:
A body has zero velocity and non- zero acceleration. It is possible as at the time when a body thrown upwards is at the top of the height. In that case velocity is zero but acceleration is equal to g.
A body travels with northward velocity but southward acceleration . it is also possible as in case when a body is going with northward velocity but when break is applied acceleration becomes southward.
A body travels with northward velocity and northward acceleration . it is also possible as in case when a body is going with northward velocity and when accelerator is applied . Acceleration becomes northward.
A body travels with constant velocity and a constant non zero acceleration . It is not possible . When there is acceleration , there must be a a change in velocity either in terms of magnitude or direction or both.
A body travels with a constant acceleration and a time varying velocity. It is possible. Time varying velocity represents acceleration.