Q. In Young’s double slit experiment with monochromatic light of wavelength 600 mm, the distance between slits is $10^{- 3}$ m. For changing fringe width by $3 \times 10^{- 5}$ m

A) The screen is moved away from the slits by 5 cm
B) The screen is moved by 5 cm towards the slits
C) The screen is moved by 3 cm towards the slits
D) Both (a) and (b) are correct
Explanation

(d) $\beta = \frac{D}{d}\lambda$
$\mathrm{\Delta}\beta = \frac{\mathrm{\Delta}D}{d}\lambda$
$\Delta D = \frac{d\Delta\beta}{\lambda}$
$= \frac{10^{- 3} \times 3 \times 10^{- 5}}{600 \times 10^{- 9}}$
$= 5\ cm\ $away or towards the slits

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

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