An object 4 cm high is placed 15 cm from a concave mirror of focal length 5 cm. The size of the image is?
-
2 cm
- 3 cm
- 4 cm
- 5 cm
The correct answer is: A
Explanation
(1)/v + (1)/u = (1)/f
(1)/v + (1)/15 = (1)/5
(1)/v = (1)/5 - (1)/15 = (3 - 1)/15 = (2)/15
∴ v = (15)/2 = 7.5 cm
magnification = (v)/u = (image size)/object size
(7.5)/15 = (X)/4
∴ image size. X = (7.5 x 4)/15 = 2 cm
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