Question

When light enters from air to water, then its frequency
A. Increases and speed decreases
B. Is same

Answer 1

light always travels in a straight line. When it strikes an obstacle, it changes its straight path. When light reflects in the same medium it is called scattering of light. When the light goes from one medium to another it is known as refraction of light.

Complete step by step solution:
When light passes from one medium to another, part of it is reflected in the same medium, and the remaining passes into the other medium. When it enters the other medium its path gets deviated, either it bends towards the normal or away from the normal. This phenomenon is called the refraction of light.
We have the following relation.
speed= frequency x wavelength.
From the formula, we can conclude that frequency will remain constant if speed and wavelength are directly proportional. So, if speed will increase then wavelength will also increase, and if speed decreases then wavelength also decreases.
Frequency only depends on the source of light. Therefore, Frequency remains constant when light travels from one medium to another medium but wavelength and speed change. Frequency is independent of medium but speed and wavelength depend on the medium.
Hence, option (B) is the correct option.

Note:
When light passes from a rarer medium to a denser medium the ray bends towards the normal. Speed and wavelength decrease when they pass from rarer to denser.
When light passes from denser medium to rarer medium the ray bends away from the normal. Speed and wavelength increase when they pass from denser to rarer.
Frequency is the number of times an event repeats itself per unit time.
SI unit of frequency is hertz, speed is meter/second and wavelength is meter.