A person far point is 2 m and his near point is 50 cm . Find the nature, focal length and power of the lenses he must use to (a). See distant objects and (b) read a book clearly. The least distance of distinct vision is 25 cm.
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( A ). To see distant objects :
The distance of the far point ( x ) = 2 m.
Where m is metre.
The defect can be corrected by using concave lens of focal length,
f = - x = - 2 m.
The power of the lens is given by :
P =
=
=
( B ). To read a book :
Here D = 25 cm.
The distance of a near point ( x ) = 50 cm.
Where cm is centimetre.
The defect can be corrected by using convex lens of focal length:
f =
=
= 50 cm.
The power of the lens given by:
P =
=
=
#Be Brainly.
:
( A ). To see distant objects :
The distance of the far point ( x ) = 2 m.
Where m is metre.
The defect can be corrected by using concave lens of focal length,
f = - x = - 2 m.
The power of the lens is given by :
P =
=
=
( B ). To read a book :
Here D = 25 cm.
The distance of a near point ( x ) = 50 cm.
Where cm is centimetre.
The defect can be corrected by using convex lens of focal length:
f =
=
= 50 cm.
The power of the lens given by:
P =
=
=
#Be Brainly.
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