Geometrical OpticsVery Hard
Question
A beam of light converges to a point P. A device L is placed in the path of the convergent beam 12 cm from P as shown. Choose the correct option(s) :-
Options
A.If L is a convex lens of focal length 20 cm, the beam converges at a point at 4.5 cm distance from P
B.If L is a convex lens of focal length 20 cm, the beam converges at a point at 10 cm distance from lens
C.If L is a concave lens of focal length 16 cm, the beam converges at a point at 48 cm distance from lens
D.If L is a plane mirror the beam converges at a point at 24 cm distance from P.
Solution
(A) If L is convex & focal length 20
f = - 20 u = + 12 ⇒ v = + 7.5
(C) If L is concave lense than f = + 16
u = + 12 ⇒ v = + 48
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