A simple microscope forms an image 10cm from an eye close to the lens. If the object is 6cm from the eye, calculate the focal length of the lens
-
3.75cm
- 4.00cm
- 15.00cm
- 16.00cm
The correct answer is: A
Explanation
Given: u = -6 cm (the object is 6 cm from the eye, and the direction is negative), v = 10 cm (the image is 10 cm from the eye)
Using the lens formula: \(\frac{1}{\text{f}}\) = \(\frac{1}{\text{v}}\) - \(\frac{1}{\text{u}}\)
\(\frac{1}{\text{f}}\) = \(\frac{1}{10}\) + \(\frac{1}{6}\)
\(\frac{1}{\text{f}}\) = \(\frac{8}{\text{30}}\)
So that f = 3.75cm upon cross multiplying
Therefore, the focal length of the lens is 3.75 cm.