Question

Q.1 A) Select the appropriate option from the given below.
1)The focal length of a
lens is positive.
a)concave
b)convex
c) focal
d) bifocal
2)The minimum distance of distinct vision for a normal human eye is
a)30cm
b)25cm
c)35cm
d)45cm
3)The focal length of a lens with power 2.5D is​

Answer 1

Answer:

ANSWER NUMBER 1) In actuality, there are two focal points for every lens, the same distance from the lens, on opposite sides. The distance from the lens to the focal point is called the focal length. For converging lenses, the focal length is always positive, while diverging lenses always have negative focal lengths.

ANSWER NUMBER 2) The minimum distance from the eye at which an object appears to be distinct is called least distance of distinct vision or near point. It is about 25 cm for human eye.

ANSWER NUMBER 3) we know that power P=2.5D

we know that power P=2.5D P=

we know that power P=2.5D P= f

we know that power P=2.5D P= f1

we know that power P=2.5D P= f1

we know that power P=2.5D P= f1

we know that power P=2.5D P= f1 f=

we know that power P=2.5D P= f1 f= 2.5

we know that power P=2.5D P= f1 f= 2.51

we know that power P=2.5D P= f1 f= 2.51

we know that power P=2.5D P= f1 f= 2.51 =0.4m=40cm

we know that power P=2.5D P= f1 f= 2.51 =0.4m=40cmSince the focal length of lens is positive so it is a convex lens. It is a converging lens.

Explanation:

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Answer 2

Answer:

( 1 ) b) convex

( 2 ) b) 25cm

( 3 ) 40cm, convex lens