A convex lens has a thick center and thin edges, forming a real, inverted image on a wall. A concave lens has a thin center and thick edges, not forming a clear image on the wall. Experiments show that a convex lens converges light rays, while a concave lens diverges light rays. Lenses are used in eyeglasses, microscopes, telescopes and other devices to magnify or correct vision.

3. Lens with a thick central portion and
a thin edge is Called convex lens
and lens with a thin central portion and
a thick edge is called concave lens.

4. Experiment
Hold a convex lens against a distant
object and try to capture the image
On a wall. Try increasing and decreasing
The distance between the lens and
the wall.
A clear inverted
image is obtained on the wall.
Repeat the experiment using a concave lens.
The image cannot be caught on
the wall.

5. Using a convex lens a real and inverted image is obtained.
Using a concave virtual, upright and
small image is formed.

6. Experiment
Fill smoke using an agarbathi
stick, inside a transparent box, to make the
path of light rays clearer. send light beams into
the box using two laser torches. We can see the
light travelling in a straight line.
Place a convex lens in the path of light,
inside the box.
Observe the changes in the path of light.
➢ Repeat the experiment using a concave
lens,and observe the change.

7. A convex lens brings the light rays passing
through it close to each other (converges).
A concave lens separates the light rays
passing through it (diverges).

8. Uses of lenses
●We use different types of spectacles to rectify defects
of vision. Different types of lenses are used in them.
• To see tiny letters and objects in a bigger size, we use
hand lens. This is a convex lens. Convex lens is used
in equipment like microscope, telescope,
camera and projector.