Question

Colour in thin films are seen due to:
1. polarisation of light
2. diffraction of light
3. interference of light
4. refraction of light

Answer 1

Correct Answer - Option 3 : interference of light

CONCEPT:

Property	Definition
Diffraction	It is the phenomenon of bending of light from the sharp corners of a slit or obstacle and spreading into the region of the geometrical shadow
Polarization	The phenomenon of restricting light waves into a single plane is called Polarization. It can be seen only in transverse waves.
Refraction	The bending of the ray of light passing from one medium to the other medium is called refraction.
Interference	When two light sources from different coherent sources meet together, then there is a distribution of energy is disturbed by each other this superposition of two light waves is called Interference of light waves.

EXPLANATION:

• When light rays strike the top surface of the thin film, some of them are reflected back to air, while others are refracted through the film.
• And this refracted ray travel through this layer of thin films and are subsequently reflected by the bottom surface of the film.
• In other words, some of the light rays travelled less of a distance than others to reach your (the observer’s eyes), so there is a difference in the length of the path.
• This path difference will lead to constructive and destructive interference which leads to the appearance of colourful patterns and we can see seven colour spectrums.

• Thus, due to the interference of light, colour in thin films is seen when illuminated with white light. So option 3 is correct.