By what factor will the size of an object placed 10cm fro...
By what factor will the size of an object placed 10cm from a convex lens be increased if the image is seen on a screen placed 25cm from the lens?
15.0
2.5
1.5
0.4
Correct answer is B
Form the lens formula = 1/U + 1/V = 1/f
=> 1/10 + 1/25 = 1/f;
∴ (5 + 2) / 50 = 1/f
∴ f = 50/7cm
since the image is observed on a screen, it is a real image. Thus magnification
M = f/U-f
| = | __50/7 |
| 10 - 50/7 |
| ∴ M = | 50/7 |
| 20/7 |