Question

Soap bubble appears coloured due to the phenomenon of :-
A. Total internal reflection
B. Interference by division of amplitude
C. Interference by division of wavefront
D. Diffraction of light

Answer 1

Hint:We are asked to find the phenomenon involved in colour formation in the soap bubble. First, understand how a soap bubble appears to be coloured, try to understand the reason and use the concept of interference to select the appropriate answer.

Complete answer:
We are asked to find which phenomenon is involved in formation of colour in soap bubble.First let us know how soap bubbles appear colored. When light enters a soap bubble some part of the light gets reflected from the outer surface and some part of the light gets refracted and enters inside and gets reflected from the other inner surface of the soap bubble.

Therefore, there are two sets of light waves that travel back to our eyes. These two sets of waves combine together or we can say there is interference of waves. Waves travel in the form of wavefronts, therefore there is division of wavefronts when the light waves come out of the soap bubble which is why the soap bubble appears to be coloured.Therefore, soap bubble appears coloured due to the phenomenon of interference by division of wavefront.

Hence, the correct answer is option C.

Note: Interference is a phenomenon in which two waves are superimposed and the resultant wave has the same, greater or lower amplitude. Students sometimes get confused between interference by division of amplitude and interference by division of wavefront. In interference by division of amplitude the incident beam is divided into two or more parts with different amplitudes and after travelling different paths they are combined together to produce interference.