Lens Equations – Examples (Part 2)

Table of Contents

• Example 1
• Example 2
• What’s Next?

In the previous segment, we looked at some Examples based on the lens equation. In this segment, let us look at some more examples of the lens equation.

Example 1

Q. A concave lens has a focal length of 18 cm. At what distance from the lens should the object be placed so that it forms an image at 9 cm from the lens?

Solution:

Given:

Distance of the image from the lens (v) = -9 cm Focal length of the concave lens (f) = -18 cm To find:

Distance of the object from the lens (u)

Formula:

1 1 1

= −

? ? ?

Solution:

1 1 1

= −

? ? ?

1

∴ =

−18

1 1

−

−9 ?

1 1 1

∴ = +

? −9 18