At sunrise and sunset the sun appears reddish due to

The correct answer is Option (1) → scattering of light

At sunrise and sunset, sunlight travels a much longer path through the atmosphere to reach us. Air molecules scatter short wavelengths far more strongly (Rayleigh scattering, intensity \( \propto 1/\lambda^{4} \)), so most of the blue light is scattered out of the beam on the way. The light that reaches us directly is rich in the longer red wavelengths.

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 – “… At sunset or sunrise, the sun’s rays have to pass through a larger distance in the atmosphere (Fig. 9.28). Most of the blue and other shorter wavelengths are removed by scattering. The least scattered light reaching our eyes, therefore, the sun looks reddish. This explains the reddish appearance of the sun and full moon near the horizon.”