A magnifying lens has a focal length of 100 mm. An object whose size is 16 mm is placed at some distance from the lens so that an image is formed at a distance of 30 cm in front of the lens.

(a) What is the distance between the object and the lens?

(b) Where should the object is placed if the image is to form at infinity?

In order to obtain a magnification of, -0.75 with a convex lens of focal length 8 cm, the object should be placed:

A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distanced the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.

(a) Rewrite the image distance in the correct order.

(b) What would be the image distance if the object distance was 90 cm?

(c) Which of the object distances gives the biggest image?

(d) What of the focal length of this lens?

A lens forms a real image 3 cm high of an object 1 cm high. If the separation of object and image is 15 cm, find the focal length of the lens.

An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is armed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.