Lens Family

Description:

A transparent medium which has at least one side curved is known as Lens.

Lens can be divided many into two families −

• Convex lens.
• Concave lens.

Convex lens

Lens which are thick at the center and thin at the edges are known as convex lens.

Convex lens concentrate the incoming parallel ray at a single point, this phenomenon is known as converging, hence convex lens are also known as converging lens.

Convex lens have different members in its family −

• Double convex

  The lens which has both the surfaces as convex is known as double convex lens.

• Plano convex

  The lens which has one side as plane surface and other as convex is known as Plano convex lens.

• Concavo convex

  The lens which has one surfaces as concave and other as convex is known as concavo convex lens.

Concave lens

Lens which are thin at the center and thick at the edges are known as concave lens.

Concave lens spread out the incoming parallel ray, this phenomenon is known as diverging, Hence concave lens are also known as diverging lens.

Concave lens have different members in its family −

• Double concave

  The lens which has both the surfaces as concave is known as double concave lens.

• Plano concavo

  The lens which has one side as plane surface and other as concave is known as Plano concave lens.

• Convex concave

  The lens which has one surfaces as convex and other as concave is known as convexo concave lens.

Focus

For a converging lens, the point at which all the rays meet after refracting from lens is known as focus.

For a diverging lens, the point from which all the diverged rays appear to come is known as focus.

Focal length depends upon the bending power of a lens. More will be the bending power, lesser will be the focal length and less will be the bending power, grater will be the focal length.

Relationship between power of lens and focal length is given by −

P = 1/f

Where,

P = Power of lens.

f = focal length.