Which of the following is true for the eye defect known as hypermetropia (farsightedness)?

What is the complementary color of red?

Account for the following:
$(a)$ Part of the human eye that helps in changing the focal length of the eye lens.
$(b)$ The condition resulting due to the eye lens becoming cloudy.
$(c)$ The factors on which the colour of the scattered white light depends.
$(d)$ The range of vision of a normal eye.
$(e)$ The sky appears dark to the astronauts in space.

The bluish colour of water in deep sea is due to

Name the colours of the visible spectrum.

Due to atmospheric refraction, the sun is visible about $2$ minutes before the actual sunrise and about $2$ minutes after the actual sunset. By how much time is the day lengthened due to this phenomenon?