Two coherent point sources S 1 and S 2 vibrating in phase emit light of wavelength λ . The separation between the sources is 2 λ . Consider a line passing through S 2 and perpendicular to the line S 1 S 2 . What is the smallest distance from S2 where a minimum of intensity occurs?

Question

Philoid · Accepted Answer

The following diagram describes the situation.

Here, forms a right angled triangle.

The path difference is {from Pythagoras theorem}

To have a minimum at O, the path difference should be .

Therefore,

Squaring both sides,

Now, for n=0,

for n=1,

for n=2,

As negative values are not allowed, the minimum values is .

Two coherent point sources S1 and S2 vibrating in phase emit light of wavelength λ. The separation between the sources is 2λ. Consider a line passing through S2 and perpendicular to the line S1S2. What is the smallest distance from S2 where a minimum of intensity occurs?

Two coherent point sources S₁ and S₂ vibrating in phase emit light of wavelength λ. The separation between the sources is 2λ. Consider a line passing through S₂ and perpendicular to the line S₁S₂. What is the smallest distance from S2 where a minimum of intensity occurs?