Question

(a) A lens is a an
(i) image forming device
() image diminishing device
(ii) image reflecting device
(iv) image refracting device


(b) Power of a lens is +3 D. What is the nature and focal length of this lens?
(i) Convex. +25 cm
(i) Concave, -25 cm
(iii) Biconcave, +25 cm
(iv) Plano-convex


(c) For which lens the magnification is always positive?
(i) Concave
(ii) Convex
(iii) Biconcave
(iv) Biconvex


(d) The focal length of a lens of power -25 D is
(i) -0.40 m
(1) - 4.0 m
(iv) -0.44 m


(e) A lens is made by joining a concave lens of focal length 80 cm and a convex lens of
focal length 40 cm. What is the power of combination of lenses?
(iv) -3.75 D
(i) -1.25 D
() +1.25 D
(1) +3.75 D​

Answer 1

Answer:

image diminishing device

concave -25cm

convex

-0.44m

-3.75D