In a double slit experiment the angular width of a fringe is found to be `0.2^(@)` on a screen placed I m away. The wavelength of light used in 600 nm. What will be the angular width of the fringe if the entire experimental apparatus is immersed in water ? Take refractive index of water to be `4//3`.

Explanation

Distance of the screen from the slits ,D=1m
wavelength of light used ,`lamda_(1) =600 nm`
Angular width of the fringe in ` air thera_(1) = 0.2 ^(@)`
Angular of the fringe in water `= theta_(2)`
Refractive index of water `mu =(4)/(3)`
Refactive index is related to angular width as :
`mu =(thata_(1))/(thera_(2))`
`theta _(2) =(3)/(4)theta_(1)`
`=(3)/(4) xx0.2 =0.15 `
therefore , the angluar width of the fringe in water will reduce to `0.15 ^(@)`