Question

What is the focal length of the convex lens used? Give reason to justify your answer.

Hint:

In ray diagrams for convex lenses, light rays diverging from an object parallel to the optical axis are refracted through the focal point on the opposite side.

Answer 1

- To determine the focal length of the lens, we need to use the lens formula: \[ \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \] Where \( f \) is the focal length, \( v \) is the image distance, and \( u \) is the object distance. 
- From the table, we can observe that as the object distance (\( u \)) decreases, the image distance (\( v \)) increases.
- This behavior is characteristic of a converging (convex) lens and suggests that the object is placed outside the focal length, but the exact focal length can be deduced if specific values for \( u \) and \( v \) are considered. Given the data, the image moves further as the object distance decreases, which is consistent with a convex lens having a positive focal length.