$A$ person cannot see distinctly objects kept beyond $2\, m$. This defect can be corrected by using a lens of power ........ $D$.

State the function of the pupil and ciliary muscles.

$A$ beam of white light falling on a glass prism gets split up into seven colours marked $1$ to $7$ as shown in the diagram.
$(a)$ The colours at positions marked $3$ and $5$ are similar to the colour of the sky and the colour of gold metal respectively. Is the above statement made by the student correct or incorrect? Justify.
$(b)$ Which of the above shown positions corresponds approximately to the colour of:
$(i)$ a brinjal
$(ii)$ danger signal
$(iii)$ neel (indigo) which is applied to clothes
$(iv)$ orange

What is the cornea?

$A$ person is unable to read a book clearly when kept at a distance of $25 \,cm$ from his eye. Name the defect. How can it be corrected? Draw ray diagrams for $(i)$ defective eye $(ii)$ corrected eye and explain them.

Name the essential parts of the human eye.