Question

One student uses a lens of focal length +25 cm and another of –25 cm. State the nature and find the power of each lens. Which of the two lenses will always give a virtual, erect and diminished image irrespective of the position of the object ?

Answer 1

Answer:

the lens of focal length +25 cm is convex and the lens with -25 cm focal length is concave.

P=1/F

for convex lens

P=1/25

P=0.4 D

for concave lens

P=1/-25

P= -0.4 D

the concave lens will always give a virtual, erect and diminished image irrespective of the position of the object

Explanation: