Question

Using formulas, explain how and why the colours of a soap bubble floating in the air change continually? What thickness or soap film would ensure that all the transmitted light interferes constructively? Explain

In radio wave production, the frequency of the wave is:

a) equal to the oscillating frequency of the electron

b) double the oscillating frequency of the electron

c) half the oscillation frequency of the electron

d)independent of the oscillation frequency of the electron.

Answer 1

dear student

You have asked multiple (3) question in this and in such cases we are instructed to answer the first question .

so i am providing you with explanation of the first part.

EXPLAINATION -:

A soap bubble consist of two films ,one on outside and one inside.Some part of light gets reflected by the inside film while some by the outside film.The reflected rays from both the films undergo interference with each other .

If rays meet with each other in same phase(i.e. phase difference is multiple of radian) then interference is constructive while if these two rays meet in opposite phase (i.e. phase difference are etc) then interference is destructive.

We know white light is made up of 7 different colors each having a characteristic wavelength, since the white light falls with different angles on the bubble , the path difference between rays will be different ,so for some angle constructive interference takes place while for others destructive .

This is the reason we see color of floating bubble changing continously .

MATHEMATICALLY

for constructive interference , t is thickness of the film

for destructive interference

hope this helps for the first part