Question

If the frequency of light, emitted by a source in an interference experiment, is made four times then the fringe width will become

• A. four times
• B. three times
• C. one fourth
• D. half

Answer 1

Answer: (C)

one fourth

Fringe width $\beta =\frac{D\lambda }{d}$
But, $\lambda \propto \frac{1}{\nu }$
When frequency becomes 4 times, wavelength becomes $\frac{1}{4}$th.
Hence ${\beta }^{\prime }=\frac{1}{4}\beta$