CBSE 2025 · Region 2 · Set 3 · Q18 · 2 marks
In a double slit experiment, it is observed that the angular width of one fringe formed on the screen is $\displaystyle 0.2^{\circ}$. The wavelength of light used in the experiment is $\displaystyle 500$ nm . Calculate the separation of the two slits.
Marking-scheme solution
Angular width $\displaystyle (\theta)=\frac{\lambda}{d}$
$\displaystyle d=\frac{\lambda}{\theta}$
$\displaystyle =\frac{500 \times 10^{-9}}{0.2 \times \dfrac{\pi}{180}}$
$\displaystyle d=\frac{45}{\pi} \times 10^{-5} \mathrm{~m}$
$\displaystyle =0.14 \mathrm{~mm}$
Wave OpticsInterference of Light Waves and Young’s ExperimentApplyvery_short_answereasy
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CBSE Class 12 Physics past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.