Question

In young's double-slit experiment if yellow light is replaced by blue light, the interference fringes become.

• A. wider
• B. narrower
• C. brighter
• D. darker

Answer 1

Answer: (B)

narrower

Fringe width of the fringes formed $\beta =\frac{\lambda D}{d}$

$⟹$ $\beta \propto \lambda$

As yellow light has larger wavelength than blue light i.e. ${\lambda }_y>{\lambda }_b$

We get ${\beta }_y>{\beta }_b$

Thus fringe width of the fringes formed by yellow light is more than that formed by blue light. Hence the interference fringes become narrower.