Question

Yellow light emitted by sodium lamp in Young’s double slit experiment is replaced by monochromatic blue light of the same intensity

• A. Fringe width will decrease
• B. Fringe width will increase
• C. Fringe width will remain unchanged
• D. Fringe will become less intense

Answer 1

The correct option is A Fringe width will decrease

Fringe width $\beta$ = $\frac{\lambda D}{d}$ and ${\lambda }_b<{\lambda }_y$
Hence, fringe width $\beta$ will decrease.