Question

A single slit of width 0.20 mm is illuminated with light of wavelength 500nm. The observing screen is placed 80 cm the slit.The width of central bright fringe will be.

• A. 1 mm
• B. 2 mm
• C. 4 mm
• D. 5 mm

Answer 1

Answer: (C)

4 mm

Width of central bright fringe.
$=\frac{2\lambda D}{d}=\frac{2\times 500\times {10}^{-9}\times 80\times {10}^{-2}}{0.20\times {10}^{-3}}=4\times {10}^{-3}m=4mm$