Question

Give the essential conditions (any two) for the source to be Coherent. (b) In Young's double slit experiment, using monochromatic light of wavelength $\lambda$, the intensity of light at a point on the screen where path difference is I, is 2K units. Find out the intensity of light at a point where path difference is $\lambda /6$.

Answer 1

Let $i_1=i_2=i$

Let $\varphi$ be the difference between two light wave s

Therefore the resultant intensity

$i_R=i+i$

$=2i+2i$

$=4i$

But $4i=2k$

When path difference is $\frac{\lambda }{6}$ phase difference is $\dfrac{\pi}{3}

$IR=i+i+2\sqrt{i}$

$IR=2i+2i(-1/2)$

$=2i-2$

$=i$

$=\frac{k}{2}$