# A square has sides of length L. In the lower-right and lower-left corners there are two sources...

## Question:

A square has sides of length L. In the lower-right and lower-left corners there are two sources of light waves, one in each corner, that emit identical in-phase light waves of wavelength 8.28 m in all directions. What is the minimum value of L such that constructive interference occurs in the upper-right corner? Ignore any reflections.

## Interference in Waves:

When two waves travel simultaneously in a medium, the displacement of a point is the vector sum of the displacement produced by each wave. When the two waves superpose in same phase the resultant displacement is maximum and the interference is said to be constructive. When the two waves superpose in opposite phase the interference is said to be destructive.

Given:

The path difference, {eq}L_1 - L_2 = L \sqrt{2} - L \\ m \lambda = 0.4142L \\ {/eq}

For minimum value of 'L' , m = 1, and we get

{eq}0.4142L = 8.28\ m \\ \Rightarrow L = 20.0\ m {/eq}