Teaching BPSC बिहार माध्यमिक TGT (9 to 10) शिक्षक भर्ती 4.0 Mock Test General Science Physics Optics
Torchlight is kept 20m to the left of a convex lens, which forms an image on screen 60m to the right of the lens. What is the focal length of the lens?
1
7.5m
2
15m
3
30m
4
More than one of the above
5
None of the above