Check the correct statements on scattering of light :

S1 : Rayleigh scattering is responsible for the bluish appearance of sky.

S2 : Rayleigh scattering is proportional to  $\frac{1}{{\lambda }^4}$

when the size of the scatterer is much less than  $\lambda \text{. }$

S3 : Clouds having droplets of water (large scattering objects) scatter all wavelengths are almost equal and so are generally white.

S4 : The sun looks reddish at sunset and sunrise due to Rayleigh scattering.