# Green light of a certain wavelength is incident upon two slits separated by 2.10 \times 10^{-5}...

## Question:

Green light of a certain wavelength is incident upon two slits separated by 2.10 \times 10^{-5} m. A screen is placed 0.800 m from the slits. The distance from the central bright line to the first-order line is 19.9 mm. What is the wavelength of the light?

## Wavelength of light

Light behaves like waves and when it passes through the two slits placed closed to each other, two waves are created. When these waves fall on a screen in sync, then a bright fringe is created and when they fall out of sync then a dark fringe is created.

The screen is placed at a distance of L = 0.8 m, from the slits and the slits are separated by a distance of {eq}\rm d = 2.1 \times 10^{-5} \ m {/eq}

Distance between the central bright fringe to the first order fringe is given as:

{eq}\rm y = \dfrac{\lambda L}{d} {/eq}

{eq}\rm 19.9 \times 10^{-3}= \dfrac{\lambda \times 0.8}{2.1 \times 10^{-5}} {/eq}

{eq}\rm \lambda = \dfrac{2.1 \times 10^{-5} \times 19.9 \times 10^{-3}}{0.8} {/eq}

{eq}\rm \lambda = 522.4 \times 10^{-9} \ m = 522.4 \ nm {/eq} 