According to Rayleigh's law, the intensity of scattered light varies with wavelength $λ$ as

$∝1/λ^4$

The correct answer is Option (2) → $∝1/λ^4$

Rayleigh's Law: It explains why the sky appears blue. According to this law, the intensity of scattered light is inversely proportional to the fourth power of the wavelength of light.

Mathematical expression:

$I \propto \frac{1}{\lambda^4}$

Shorter wavelengths (like blue) scatter more than longer wavelengths (like red).