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 2 F
B
Between lens and F
C
Between F and 2F near 2F
D
Between F and 2F equidistant from F and 2F
Answer
Between F and 2F equidistant from F and 2F
Explanation
Solution
x – f = 2f – x
2x = 3f
x = 1.5f