Question

Two lenses A and B of focal length +20 and -20 cm respectively.Give the power in each case of lens.Which of the two lenses will form virtual and magnified image of an object placed 15 cm from the lens.Justify your answer

Answer 1

power of lens A=1/f(in m) or 100/f(in cm)=100/20=5D
power of lens B=100/-20=-5D
lens A and B both will form virtual and errect image as in case of A it is between f and optical centre and in B it is concave lens