Question

You have an infrared laser that produces light of an unknown wavelength.
A. You shine this laser through a mask containing a single slit of width a. On a screen that is a
distance L away, you find a very broad bright spot at the center of the screen that has a width of
L. Determine the wavelength of the laser in terms of the given quantities.
B. You shine the same laser through a different mask containing a single slit that

Answer 1

As per the question,

Slit width = a

Distance between the screen and slit = L

We know that width of the central maxima = $\frac{2\lambda D}{d}$

Now substituting the values as per the given question,

$L=\frac{2\lambda L}{a}$

Hence, $\lambda = \frac{a}{2}$

and we know that $x=\frac{2\lambda D}{d}$

Hence, $x\propto \frac{1}{d}$