Question

A monochromatic beam of light passes from a denser medium into a rarer medium. As a result

• A. its velocity increases
• B. its velocity decreases
• C. its frequency decreases
• D. its wavelength decreases

Answer 1

The correct option is A its velocity increases

From Snell's law we get $n\times v=$ constant

where $n$ is the refractive index of the medium and $v$ is velocity of light in that medium.

Since for rarer medium, the refractive index is less, so light will travel faster in in rarer medium.