Question

In Young’s double-slit experiment, the separation between the slits is halved and the distance between the slits and the screen is doubled. The fringe width will

• A. remain the same
• B. be halved
• C. be doubled
• D. be quadrupled

Answer 1

Answer: (D)

The fringe width in Young’s double-slit experiment
$\beta =\frac{\lambda D}{d}$
where $\lambda$ is the wavelength of light used
$D$ is the distance between slit and screen.
$d$ is the distance between the slit.
$\therefore {\beta }^{\prime }=\frac{\lambda (2D)}{\frac{d}{2}}=4\frac{\lambda D}{d}=4\beta$