Question

A viewing screen is separate from double slit source by 1.2m the distance between the two slits is 0.03mm the second order bright fringe (m=2)is 4.5cm from the center line .(a) determine the wavelength of the light.(b) calculate the distance between adjaseet bright fringe

Answer 1

Given,

Distance between slits and screen $\ D=1.2\ m$

Distance between two slits $d=0.03\ mm$

Second order bight fringe is 4.5 cm from center line

(a) We know,

Position of $2^{nd}$ order bright fringe

$$y_2=\dfrac{2\lambda D}{d}\\ \Rightarrow \lambda = \dfrac{y_2\times d}{2D}\\ \ \\ \Rightarrow \lambda = \dfrac{4.5\times 3\times 10^{-7}}{2.4}=562.5\ nm$$

(b.) The distance between adjacent bright fringe

$$\Delta y= \dfrac{\lambda D}{d}=\dfrac{562.5\times 10^{-9}\times1.2}{3\times 10^{-7}}=22.5\times 10^{-3}\ mm$$