Question 231: Waves Optics

Question

In a Young's double slit experiment 15 fringes
are observed on a small portion of the screen
when light of wavelength 500 nm is used. Ten
fringes are observed on the same section of
the screen when another light source of
wavelength $$\lambda $$ is used. Then the value of $$\lambda $$ is
(in nm) __________.

Accepted Answer

The length of the screen used portion for 15
fringes, and also for ten fringes
15 $$ 	imes $$ 500 $$ 	imes $$ $${D \over \lambda }$$ = 10 $$ 	imes $$ $${{\lambda D} \over \lambda }$$
$$ \Rightarrow $$ 15 ÃÂ 50 =$$\lambda $$
$$ \Rightarrow $$ $$\lambda $$ = 750 nm

Waves Optics

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