Physics
What is refractive index ?

It is defined as the product of speed of light in medium and in vacuum.
It is defined as the ratio of speed of light in the medium to the speed of light in vacuum.
It is defined as the ratio of speed of light in vacuum to the speed of light in the medium.
None of above

ANSWER DOWNLOAD EXAMIANS APP

Physics
Railway tracks are banked on curves so that

No frictional force may be produced between the tracks and the wheels of the train
Necessary centrifugal force may be obtained from the horizontal component of the weight of the train
The train may not fall down inwards
Necessary centripetal force may be obtained from the horizontal component of the weight of the train

ANSWER DOWNLOAD EXAMIANS APP