Daily life phenomena based on scattering of light are(A) Blue colour…

The correct answer is Option (1) → (A), (B) and (D) only

Small particles in the air (molecules, much smaller than the wavelength) scatter light with intensity proportional to \( 1/\lambda^{4} \) (Rayleigh scattering), so blue is scattered most and red least. Large particles such as water drops scatter all colours about equally.

(A) Blue colour of sky — Correct. Air molecules scatter the short (blue) wavelengths of sunlight much more than the long ones, and this scattered light reaches us from all parts of the sky.

(B) Clouds appearing white — Correct. Cloud droplets are much larger than the wavelength and scatter all colours almost equally, so the scattered light is white.

(C) Twinkling of stars — Incorrect. Twinkling is due to atmospheric refraction: the changing refractive index of the moving air makes the apparent position and brightness of a star flicker.

(D) Danger signals being red — Correct. Red light is scattered the least, so it passes through fog, smoke and dust with little loss and is seen from far away.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Scattering of Light – “As sunlight travels through the earth’s atmosphere, it gets scattered (changes its direction) by the atmospheric particles. Light of shorter wavelengths is scattered much more than light of longer wavelengths. … Hence, the bluish colour predominates in a clear sky, since blue has a shorter wavelength than red and is scattered much more strongly.”

Scattering of Light – “… For \( a \gg \lambda \), i.e., large scattering objects (for example, raindrops, large dust or ice particles) this is not true; all wavelengths are scattered nearly equally. Thus, clouds which have droplets of water with \( a \gg \lambda \) are generally white.”