Question

what are rarer and denser midium........

Answer 1

optically rarer medium refers to that medium in which light bends away from the normal.
here speed of light is more in comparison to an optically denser medium.
optically denser medium means that medium in which light bends towards the normal.
NOTE ---MASS DENSITY AND OPTICAL DENSITY ARE DIFFERENT THINGS...
u can take an example...... kerosene has higher optical density than water but it's mass density is lower than that of water.......