Chapter 31, Problem 20A

To determine

To rank: The distance between points C and D from greatest to least.

Answer to Problem 20A

  $A>B>C$

Explanation of Solution

Introduction:

The superposition of the two light waves can be defined as the interference of light. When the crest of the one wave overlaps with the crest of the second wave then the interference is said to be constructive. If the crest of the one wave falls on the trough of the other wave then it is said to be destructive interference.

In case of destructive interference, the distance between the regions of the destructive interference depends upon the wavelength of light and distance between the sources of the light. So, in the given three scenarios, in (A) distance between the sources is reduced with the same wavelength but the lesser the distance between the sources, the greater the distance between the regions C and D. Similarly, in case (B) the distance between the sources is increased. So, the distance between C and D will be less in this case. In case (C), the wavelength is reduced to half. This means that the distance between regions C and D will be the least in this case.

Hence, the ranking on the basis of distance between C and D is: $A>B>C$

Conclusion:

Hence, the ranking on the basis of distance between C and D is: $A>B>C$