The transduction of light into nerve impulses is a:

Which of the following statements is correct?

In mammals,which cells are responsible for colour detection in the retina?

Which of the following statements is correct regarding the pupil of the human eye?
$(I)$. It is the aperture surrounded by the iris.
$(II)$. The diameter of the pupil is regulated by the muscle fibres of the iris.
$(III)$. It is a transparent crystalline structure attached to the ciliary body.
The correct option is:

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

Define the location and function of the following structures:
$(1)$ Epithalamus
$(2)$ Rod cells