Question

State two differences between a convex and concave lens.

Answer 1

Hint: When two concave mirrors join with each other, a concave lens is formed and it is also applicable for convex mirror and lens. Both are having characteristics about light divergence and convergence exactly opposite to that of a mirror.

Complete answer step by step:
First we see what is meant by lens. Lens is an optical tool which converges or diverges a light beam by refraction. It is made from a transparent material.
Here we see some lenses which are known based on their shapes and properties namely convex and concave.
Let us see what a convex and concave lens is.

Convex lens: The lens which converges the light beam after passing through it. It has thin upper and lower edges and the middle part is thick. It is also known as a converging lens.

Concave lens: The lens which diverges the light beam after passing through it. It has its external surface curving inside. It is also known as a diverging lens.

Difference between convex and concave lens:

1. On passing the light through a convex lens, the light beams meet at one point; it means they converge and so it is a convergent lens. While on passing the light through a concave lens, light beams diverge and are known as diverging lenses.
2. A convex lens has thin edges with a thicker centre while a concave lens has thick edges with thinner centre.
3. Due to the positive focal length convex lens is termed as positive lens while due to the negative focal length concave lens is termed as negative lens.
4. Convex lens is useful to cure long-sightedness and a concave lens is used to cure short-sightedness.

Note: Always remember both the lenses by remembering the convex and concave mirrors. Convex mirror diverges the light while a convex lens converges the light. Concave mirror converges the light while a concave lens diverges the light. So, it is easy to remember, one can only keep the information about the mirror and according to that, but in opposite characteristics, remember the lens.