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Wave Optics — Physics STD 12 Science — Question

Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsWave Optics3 Marks
Question
In Young's double-slit experiment, the second minimum in the interference pattern is exactly in front of one slit. The distance between the two slits is $d$ and that between the source and screen is $D$. What is the wavelength of the light used?
✓

Answer

The distance of the mth minimum from the central fringe is,
$
y_n=(2 m-1) \frac{\lambda D}{2} d
$
Given, $y_{2 a}=\frac{d}{2}$ for $m=2$
$
(4-1) \frac{\lambda}{2} \frac{D}{d}=\frac{d}{2} \quad \therefore 2=\frac{d^2}{3 D}
$
This is the wavelength of the light used.

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