Question

In Young's double-slit experiment, the slits are 0.2 mm apart and the screen is 1 m away. The distance between the central bright fringe and the third bright fringe is 1.5 cm. The wavelength of light used is:

• A. 500 nm
• B. 600 nm
• C. 700 nm
• D. 400 nm

Hint:

Fringe distance is proportional to order number.

Answer 1

The Correct Option is A

\[ y_n = n\frac{\lambda D}{d} \Rightarrow \lambda = \frac{yd}{nD} = \frac{0.015\times0.0002}{3\times1}=5\times10^{-7}\ \text{m} \]