The speed of light changes as it enters from one medium to another as the optical density of the medium changes.
The change in speed of light as it travels through various media are depicted in the following table.


Which of the following represents correct descending order of optical densities of the media.

Correct option is A

The correct answer is A> D> C>B.
Refraction of Light:
When a ray of light propagating in a medium enters the other medium, it deviates from its path. This phenomenon of change in the direction of propagation of light at the boundary, when it passes from one medium to another medium, is called the refraction of light.
When a ray of light enters from a rarer medium to a denser medium (air to water) it deviates towards the normal drawn on the boundary of two media at the incident point.
• The entity that doesn't change is the frequency.
• The entity that changes are wavelength and velocity.
• The retractive index is also equal to the velocity of light c of a given and the wavelength in empty space divided by its velocity v in a substance
• Thus, Velocity, Wavelength & Refractive index change when light travels from one medium to another but Frequency remains unchanged.
• The optical density of a medium is inversely proportional to the speed of light in that medium. If the speed of light increases as light travels from medium A to medium B, then medium B must be less optically dense the medium A Similarly, if the speed of light decreases as light travels from medium B to medium C., then medium C must be more optically dense than medium B.