Notifications
Clear all
Light Reflection and Refraction
1
Posts
2
Users
0
Likes
437
Views
0
18/08/2021 12:20 pm
Topic starter
An erect image 2.0 cm high is formed 12 cm from a lens, the object being 0.5 cm high. Find the focal length of the lens.
1 Answer
0
18/08/2021 12:24 pm
\(h_2\) = 2 cm (Erect image)
v = -12 cm (Erect image)
\(h_1\) = 0.5 cm
m = \(\frac{v}{u}\) = \(\frac{h_2}{h_1}\)
\(\frac{-12}{u}\) = \(\frac{2}{0.5}\)
u = -3 cm
\(\frac{1}{v}\) - \(\frac{1}{u}\) = \(\frac{1}{f}\)
\(\frac{1}{-12}\) - \(\frac{1}{-3}\) = \(\frac{1}{f}\)
\(\frac{-1 + 4}{12}\) = \(\frac{1}{f}\)
f = 4 cm