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A convex lens (of focal length 20 cm) an...

A convex lens (of focal length 20 cm) and a concave mirror, having their principal axes align the same lines, are kept 80 cm apart from each other. The concave mirror is to the right of the convex lens. When an object is kept at a distance of 30 cm to the left of the convex lens, its image remains at the same position even if the concave mirror is removed. The maximum distance (in cm) of the object for which this concave mirror, by itself would produce a virtual image would be:

A

10 cm

B

20 cm

C

25 cm

D

30 cm

Text Solution

Verified by Experts

The correct Answer is:
A
Using lens formula
`(1)/(v) - (1)/(-30) = (1)/(20) rArr v = 60 cm `
Distance of this image from Mirror is 20 cm . As per given condition image should from at COC of mirror. So that 20 cm `= 2 f_(M) rArr f_(M) = 10 cm `
Hence Maximum distance from mirror for virtual image is focal length = 10 cm
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