In cataract:

Answer briefly:
$(a)$ How do you perceive the colour of an object?
$(b)$ Which part of our body helps us in maintaining the body balance?
$(c)$ How does the eye regulate the amount of light that falls on the retina?

The following figure is a diagram showing parts of the human eye. Identify $P, Q$,and $R$ from the options given below.
$\quad\quad P\quad\quad\quad Q\quad\quad\quad R$

Aqueous humor and vitreous humor are secreted by .....

Which part of the eye controls the amount of light entering into it?

In the human eye,the image formed on the retina is: