A convex lens has power +4 D. Its focal length is
A0.4 m
B4 m
C2.5 m
D0.25 m
Answer & Solution
Correct answer: D. 0.25 m
$f=1/P=1/4=0.25$ m. Positive power confirms a convex (converging) lens.
Related questions
For a concave mirror, as an object moves from infinity towards the focus, the real imageThe power of a lens is −2.5 D. The lens isA small bulb is placed at the focus of a concave mirror of focal length 12 cm. The reflectWhich mirror is used as a rear-view mirror in vehicles, and why?An object 4 cm tall is placed 15 cm from a convex lens of focal length 10 cm. The image heA ray of light travelling in air enters water (n = 4/3). It bendsThe laws of reflection hold good forA convex lens forms a real image three times the size of the object on a screen. If the fo