Question

The fringe width for red colours as compared to that for violet colour is approximately

• A. 3 times
• B. double
• C. 4 times
• D. 8 times

Answer 1

Answer: (B)

As ${\lambda }_r\approx 8000A^{\circ }$ and ${\lambda }_v\approx 4000A^{\circ }$ and $\beta =\frac{\lambda D}{d}$ i.e.
$\beta \propto \lambda ,$ therefore ${\beta }_{red}$ is roughly double of ${\beta }_{violet}$