Exercise

Give scientific reason:

One can sense colours only in bright light.

Give scientific reason:

We cannot clearly see an object kept at a distance less than $25 \mathrm{cm}$ from the eye.

Distinguish between:

Farsightedness and Nearsightedness

Distinguish between:

Concave lens and Convex Lens

What is the function of iris and the muscles connected to the lens in human eye?

The doctor has prescribed a lens having power $+1.5 \mathrm{D}$. What will be the focal length of the lens? What is the type of the lens and what must be the defect of vision?

$5 \mathrm{cm}$ high object is placed at a distance of $25 \mathrm{cm}$ from a converging lens of focal length of $10 \mathrm{cm}$. Determine the position, size and type of the image.

Three lenses having power $2$, $2.5$ and $1.7 \mathrm{D}$ are kept touching in a row. What is the total power of the lens combination?