Question

The optician's prescription for a spectacle lens is marked+ 0.5 D. What is the: (a) nature of spectacle lens?; (b) focal length of spectacle lens ?

Answer 1

Explanation:

Positive power indicates it is a converging lens.

Power of a lens is given by:

power(p)=

1

f

1f

0.5

=

1

f

0.5=1f

f

=

1

0.5

f=10.5

f

=

2

m

f=2m

Answer 2

Explanation:

Nature Of The Spectacle Lens:Converging Lens Or Virtual (Power Is Positive)

Focal Length :

P(Power)=1(m)/f

As Given,

P = +0.5

Then,

0.5 D = 1/f

f = 1/0.5

f= 2m or 200 cm