Question

(a) A lens is a an
(i) image forming device
(ii) image diminishing device
(iii) 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 -2. 5 D is
(i) -0.40 m
(ii) - 4.0 m
(iii) - 0.04 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?
(i) - 1.25D
(ii)+1.25D
(iii)+3.75D
(iv)-3.75D​

Answer 1

Answer:

Image obtained is virtual, erect and diminished in case of concave lens.