Question

In biprism experiment, the distance of 20th bright band from the centre of the interference pattern is 8 mm. The distance of the 30th bright band is

• A. 4 mm
• B. 8 mm
• C. 12 mm
• D. 16 mm

Answer 1

The correct option is C 12 mm

Given

$20\frac{\lambda D}{d}=8=\frac{\lambda D}{d}=\frac{8}{20}\therefore {30}^{th}$ bright,

$=30\times \frac{\lambda D}{d}=30\times \frac{8}{20}=12mm$