Question

1. How far from a convex lens of focal length 25.0 cm must an object be placed to produced an image that is upright and magnified twice?
2. What is the resulting focal length and power if two thin lenses of focal length

+ 25cm and -50 cm are in contact?

Answer 1

1.

$d=2f=50~cm.$

2.

$F=\frac{fd}{f-d}=16.7~cm.$