VISUAL PHYSICS ONLINE

3.1 WAVES

P31 014

In an experiment to determine the focal length of a thin glass lens, it is found that when a luminous object is placed 300 mm from the lens, a well-focused image is formed on a screen 200 mm from the lens.

(A)

What kind of lens must be used in this experiment? Justify your answer.

(B)

Calculate the focal length of the lens.

(C)

Draw a diagram of the lens arrangement (approximately to scale).

View solution below only after you have completed answering the question. The solution is not in a form that you would answer in an examination. The answers are often in more detail to help improve your appreciation and understanding of the physics.

Solution

Knowledge thin lenses

(A)

A convex lens is used because a real, well focused image is formed on a screen, and real images are only formed by convex lenses.

(B)

Thin lens equation

(C)