In a Young’s double slit experiment with Slit separation 0.1 mm, one observes a bright fringe at angle `1/40` rad by using light of wavelength `lamda_1` When the light of wavelength `lamda_2` is used a bright fringe is seen at the same angle in the same set up. Given that are in range 600 nm to 900nm, their values are:

Options

A. 600 nm, 750 nm
B. 625 nm, 800 nm
C. 600 nm, 800 nm
D. 380 nm, 500 nm

Answer

B

Explanation

`theta = y/D`
` 1/40 = (n_1 lamda_1 D/d)/(D)`
` 1/40 = (n_1 lamda_1)/(d) = (n_1 lamda_1)/(0.1 xx 10^(-3) ) rArr n_1 lamda_1 = (10^(-4))/(40) = (100000)/(40) nm = 2500 nm `
`lamda = (2500)/(n)`
` n = 1 to lamda = 2500 , n= 2 to lamda = 1250`
`n = 3 to lamda = 800 , n = 4 to lamda = 625`
` n = 5 to lamda = 500 , lamda = 625,800