Question

A convex lens forms a real image 6 times the size of the object. The distance between object and image is 33 cm. Find the focal length of the lens.
1/do + 1/di = 1/f

di/do = 6

di + do = 33

You have to solve three equations in three unknowns. Solve the last two in two unknowns first.

do + 6do = 33
do = 33/7 = 4.714 cm,
di = 28.286 cm

Now solve for f using the first equation.

f = 4.0406 cm

Related Questions

A convergent lens forms a real image 2.41 times the size of the object. The distancebetween object a... In an experiment ,an object was placed on the principal axis of a convex lens 25 centimetres away fr... A convex lens of focal length f, forms a real image whose size is the same as that of the object....