Question

a lens has a power af 0.5D

Answer 1

f = 1/d
=1/0.5
=10/5
=2 d
hypermetropia

Answer 2

Answer:

Focal length of lens = 200 cm, Convex Lens  

Explanation:

The power of lens given in the question is 0.5D

To find the focal length of lens we use the formula of  

$\text { Power }(D)=\frac{100}{f(\mathrm{cm})}$

Putting the value of Power = 0.5D, we get:

$0.5=\frac{100}{f(c m)}$

Therefore, the focal length of lens is  

$f(c m)=200$

The nature of the lens is convex; this is because convex lens has converging properties along with being positive. Hence, if the light beam has a source at an infinite length and strikes the lens, all the light beams converge at single point on a focal length.