Notifications
Clear all
Light Reflection and Refraction
1
Posts
2
Users
0
Likes
365
Views
0
20/08/2021 1:05 pm
Topic starter
An object 60 cm from a lens gives a virtual image at a distance of 20 cm in front of the lens. What is the focal length of the lens? Is the lens converging or diverging? Give reasons for your answer.
1 Answer
0
20/08/2021 1:08 pm
u = -60 cm
v = -20 cm (Virtual image)
\(\frac{1}{f}\) = \(\frac{1}{v}\) - \(\frac{1}{u}\)
\(\frac{1}{f}\) = \(\frac{1}{-20}\) - \(\frac{1}{-60}\)
= \(\frac{-2}{60}\)
f = -30 cm
The lens is diverging because the focal length is negative.