Reddish appearance of the sun at sunrise or sunset is significantly due to

What is meant by the least distance of distinct vision? How does this vary between the very young and old people?

Explain the following terms connected with the eye:
$(i)$ Ciliary muscles
$(ii)$ Accommodation
$(iii)$ Blind spot.

Mention the factor on which scattering of light depends. Why does the sky appear dark in space?

$(a)$ If a person wears a lens of power $-6\, D$ for distant vision and for correcting his near vision he needs a lens of $+2\, D$. Determine the focal length of the lenses in both the cases.
$(b)$ Give reasons for the following natural phenomena:
$(i)$ Stars twinkle.
$(ii)$ Planets do not twinkle.
$(iii)$ Stars appear raised in the sky.

What color does a red rose appear when green light is incident upon it?