Light from a helium-neon laser (? = 633 nm) is used to illuminate two narrow slits. The interference pattern is observed on a screen 3.2m behind the slits. Eleven bright fringes are seen, spanning a distance of 60mm . What is the spacing (in mm) between the slits?

0.3376 mm

Explanation:

The computation of the spacing in mm between the slits is shown below:

As we know that

where,

= wavelength

L = distance from the scrren

= spanning distance

As there are 11 bright fingers seen so m would be

= 11 - 1

= 10

Now placing these values to the above formula

So, the spacing is

= 0.3376 mm

We simply applied the above formula.