Q. In double slit experiment, the angular width of the fringes is $0.20{^\circ}$ for the sodium light $(\lambda = 5890\mathring{\mathrm{A}})$. In Order to increase the angular width of the fringes by 10%, the necessary change in the wavelength is
A) Increase of $589\ \mathring{\mathrm{A}}$
B) Decrease of $589\ \mathring{\mathrm{A}}$
C) Increase of $6479\ \mathring{\mathrm{A}}$
D) Zero
Explanation
(a) $\theta = \frac{\lambda}{d};\theta$ can be increased by increasing $\lambda$, so here $\lambda$ has to be increased by 10%
$i.e.,\%$ Increase $= \frac{10}{100} \times 5890 = 589\mathring{\mathrm{A}}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.