UPSEE Solved Model Paper 2

If an interface experiment is performed using two wavelengths close to each other, two interference patterns corresponding to the two wavelengths are obtained on the screen. The fringe system remains distinct upto a point on the screen where the nth order maximum of one wavelength , say λ1 5890

0

A

. Thus, interference patter can be seen upto a distance yn from the centre of the screen if
yn =

nλ1D

d

; (nth maximum) (1)
= (n−

1

2

)

λ2D

d

; (nth minimum) (2)
or nλ1 = (n−

1

2

)λ2 or 2nλ1 = (2n−1)λ2 which gives
n =

λ2

2(λ2−λ1)

, which is choice (3)