Question

In Young’s double-slit experiment, the slit separation is 0.4 mm and the screen is 2 m away. If light of wavelength 600 nm is used, the fringe width is:

• A. 2 mm
• B. 3 mm
• C. 4 mm
• D. 5 mm

Hint:

Always convert all physical quantities to their standard SI units (meters) before performing calculations.
Conversion factors:
$1\text{ nm} = 10^{-9}\text{ m}$
$1\text{ mm} = 10^{-3}\text{ m}$
Keeping the powers of 10 sorted makes calculations straightforward and error-free.

Answer 1

The Correct Option is B

Step 1: Fringe width.
$\beta = \lambda D/d = (600\times10^{-9}\times2)/(0.4\times10^{-3})$
\[ \boxed{\beta = 3 \text{ mm}} \]