Question

Coherent light with lambda equals 644 n m illuminates on a double slit. The white screen is 6 cm from the slits. The two slits are spaced apart by 2,783 nm. Determine the distance on the screen between the 4th and the 2nd bright fringes above the central maximum.

Answer 1

Answer: 2.77 cm

Explanation:

Given

Wavelength of light is $\lambda=644\ nm$

White screen is at a distance of $D=6\ cm$

Distance between two slits is $d=2783\ mm$

Distance between two bright fringe is $\frac{\lambda D}{d}$

So, the distance between 4 th and 2nd bright fringe is

$\Rightarrow y_4-y_2=\dfrac{2\lambda D}{d}\\\\\Rightarrow y_4-y_2=\dfrac{2\times 644\times 10^{-9}\times 6\times 10^{-2}}{2783\times 10^{-9}}\\\\\Rightarrow 2.776\times 10^{-2}\ m\\\Rightarrow 2.77\ cm$

The distance between 4 th and 2 nd brigth fringe is 2.77 cm.