In Young's double slit experiment, red light of wavelength 6000Å is used and the nth bright fringe is obtained at a point P on the screen. Keeping the same setting, the source of light is replaced by…

Question

In Young's double slit experiment, red light of wavelength 6000Å is used and the nth bright fringe is obtained at a point P on the screen. Keeping the same setting, the source of light is replaced by green light of wavelength 5000Å and now (n+1 ) th bright fringe is obtained at the point P on the screen. The value of n is

Accepted Answer

Correct answer: B. (b) Fringe width, = λDd And for n number of fringes, _G=n λDd or ; _R=n λDd For (n+1 ) th number of fringes, _G= (n+1 ) λDd ∵ _R= _G orn _RDd= (n+1 ) _RDdn .6000 10^-10 Dd= (n+1 )5000 10^-10 Dd ⇒6n= (n+1 )5 ⇒6n=5n+5 or ,6n-5n=5 ∴n=5

Solution

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