Physics Optics Help

Question

CALCULATIONS

4. A lens has a focal length of 2m. A pencil is placed 3m from the lens.

1. Where will the image of the pencil be formed?

Is the image inverted or upright? How do you know?

Answer 1

HI there,

The solution to this question really depends on what kind of lens you have.

Since you didn't include this information Ive shown you what the solution would be for either one.

If it's a converging or convex lens f = 2 m

But if it's a diverging or concave lens f= -2 m.

In either case objct distance, s_o, is given to us as 3 m.

Using the lens equation we can solve for image distance s_i.

For a converging lense s_i would be 6 m, a real image to right of lens. (Since positive s_i)

M = -6/3 = -2 therefore it's image is inverted and magnified. (Since negative M and |M|>1)

For diverging lens s_i would be -1.2, a virtual image on same side as object.

M = 1.2/3 = 0.4, therefore image is upright but smaller.