CBSE Class 10 Science 2020 · Paper 31(B) · Question 29

(a) The student suffers from myopia (near-sightedness): distant objects are not seen clearly because their image forms in front of the retina. Causes: (i) excessive curvature of the eye lens, or (ii) elongation of the eyeball. Correction: spectacles with a concave (diverging) lens of suitable power; it makes the rays from a distant object diverge as if they came from the far point of the eye, so that the eye lens brings the image onto the retina. (b) At sunrise and sunset, light from the Sun near the horizon travels through much thicker layers of air, a longer distance in the atmosphere. Most of the blue and other short-wavelength light is scattered away by the fine particles of air, while red light, which is scattered least, reaches our eyes, so the Sun appears reddish. No, an astronaut on the moon would not observe this: the moon has no atmosphere, so no scattering of light takes place, and the Sun appears white against a black sky.