When monocromatic orange light is used instead of violet light in a convex lens, its focal length will:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → increase
Since, the refractive index is wavelength dependent, for shorter wavelength (like violet), the $μ$ is higher while for larger wavelength (like orange), the refractive index is lower.
and,
$μ∝\frac{1}{f}$
Hence, when using monochromatic orange light, instead of violet light, the focal length of the lens increases.