A person cannot see any object placed beyond 50cm from his eye. Calculate the power of the lens which will enable him to see the distant stars clearly.

-1 D

No worries! We‘ve got your back. Try BYJU‘S free classes today!

+1 D

No worries! We‘ve got your back. Try BYJU‘S free classes today!

+2 D

No worries! We‘ve got your back. Try BYJU‘S free classes today!

-2 D

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

Open in App

Solution

The correct option is D -2 D
As the person cannot see the objects clearly beyond 0.5m, (or 50cm). He wants to see the distant stars clearly. To do so, he should use lens which forms the image of a distant object $(u = - \infty)$ at a distance of 50cm in front of it.

So, from lens formula,

$\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$
$\Rightarrow \frac{1}{- 50} - \frac{1}{- \infty} = \frac{1}{f}$
$\Rightarrow f = - 50 c m = - 0.5 m$
or Power P = $\frac{1}{f} = - \frac{1}{0.5} = - 2 D$

Suggest Corrections

Similar questions

Q. A person cannot see distinctly any object placed beyond 40 cm from his eye. Calculate the power of the lens which will enable him to see distant starts clearly.

Q. A near sighted person cannot see distinctly beyond

50 c m

from his eye. The power in diopter of spectacle lenses which will enable him to see distant objects clearly is:

Q. The far point of a myopic person is 80 cm. What is the power of the lens required to enable him to see the distant objects clearly?

A myopic person can see things clearly if they lie between 8 cm and 100 cm from his eye. The lens will enable him to see the moon distinctly if its focal length is:

Q. A man cannot see clearly the objects beyond a distance of 20 cm from his eyes. To see distant objects clearly the kind of lenses and its focal length must be

Join BYJU'S Learning Program