JEE Main202127 Aug 2021Morning ShiftPhysicsRay OpticsActual
Find the distance of the image from object O , formed by the combination of lenses in the figure:
Options
- A75   cm
- B10   cm
- Cinfinity
- D20   cm
Correct answer
A. 75   cm
Step-by-step solution
1 Lens formula 1 v - 1 u = 1 f , 1 v - 1 - 30 = 1 10 1 v = 1 10 - 1 30 ;    1 v = 3 - 1 30 ; v = 15   cm 2 u = + 10 1 v - 1 10 = 1 - 10 1 v = - 1 10 + 1 10    v = ∞ 3 Ray will converge at focus of 30 cm right of third lens. it. v = + 30   cm (from third lens)