Question
Question: A source of light is placed at double focal length from a convergent lens. The focal length of the l...
A source of light is placed at double focal length from a convergent lens. The focal length of the lens is f = 30 cm. At what distance from the lens should a flat mirror be placed so that ray reflected from the mirror are parallel after passing through the lens for the second time-
A
Beyond 2f
B
Between lens & f
C
Between f & 2f near 2f
D
Between f & 2f equidistant from f & 2f
Answer
Between f & 2f equidistant from f & 2f
Explanation
Solution
x – f = 2f – x
2x = 3f
x = 1.5 f