On changing the medium, the ray of light bends. This bending occurs due to __:
1. Change in speed of light
2. Change in frequency of light
3. Change in wavelength of light
Choose the correct option from the codes given below:

Answer: [C] Only 1 & 3 are correct

The first thing we have to note is that light bends when it changes medium, but when light changes the medium, it is always NOT necessary that it bends too. I will explain it. In this question, you have to remember that speed changes and also the wavelength may change but not the frequency. Change in speed is the fundamental of refraction.

Refraction is the change in direction of a wave due to a change in its speed. Due to change of medium, the phase velocity of the wave is changed but its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any angle other than 90° or 0°. If the wave passes at 90°, it’s speed will still change, its refraction would still occur but its direction will not change. This is funda behind use of lenses.

Refraction is described by Snell’s law, which states that for a given pair of media and a wave with a single frequency, the ratio of the sines of the angle of incidence θ1 and angle of refraction θ 2 is equivalent to the ratio of phase velocities (v1 / v2) in the two media, or equivalently, to the opposite ratio of the indices of refraction (n2 / n1).

Please note that refraction is a phenomenon that often occurs when waves travel from a medium with a given refractive index to a medium with another at an oblique angle. At the boundary between the media, the wave’s phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases but its frequency remains constant. For example, a light ray will refract as it enters and leaves glass, assuming there is a change in refractive index.

A ray traveling along the normal (perpendicular to the boundary) will change speed, but not direction. Refraction still occurs in this case.

This question is a part of GKToday's Integrated IAS General Studies Module