Question

The focal length of a lens is + 0.50 m. The power of the lens and type are
.(A)
+ 2.0 D and convex lens
(B) + 2.0 D and concave lens
(C) - 2.0 D and concave lens
(D) - 2.0 D and convex lens​

Answer 1

Answer:

Given,

Focal length, f=50cm

Power, P=100​/f

=50100​

P=2D

Since, focal length in +ve lens is convex.

Hope you understand

Answer 2

Given,

The focal length of lens = +0.50m

To find,

The power of lens and type of lens.

Solution,

We can simply solve this numerical problem by the following process.

Power = 1/Focal length

Power = 1/0.50

Power = + 2.0D

Now, it is given that the focal length of the lens is +0.50m, which is a positive value. Now, a positive focal length can be found only in the case of a convex lens. Which implies that, the given lens is obviously a convex lens.

Hence, the power is +2.0 D and the lens is a convex lens. (Option A)