JEE Advanced2010PhysicsRay OpticsActual
A biconvex lens of focal length 15 ~cm is in front of a plane mirror. The distance between the lens and the mirror is 10 cm . A small object is kept at a distance of 30 ~cm from the lens. The final image is
Options
- Avirtual and at a distance of 16 ~cm from the mirror
- Breal and at a distance of 16 ~cm from the mirror
- Cvirtual and at a distance of 20 ~cm from the mirror
- Dreal and at a distance of 20 ~cm from the mirror
Correct answer
B. real and at a distance of 16 ~cm from the mirror
Step-by-step solution
Object is placed at distance 2 f from the lens. So first image I₁ will be formed at distance 2 f on other side. This image I₁ will behave like a virtual object for mirror. The second image I₂ will be formed at distance 20 ~cm in front of the mirror, or at distance 10 ~cm to the left hand side of the lens. Now applying lens formula array rlr & 1 v - 1 u = 1 f & 1 v - 1 +10 = 1 +15 or & v=6 ~cm array Therefore, the final image is at distance 16 ~cm from the mirror. But, this image will be real. This is because ray of