Q.

Two concave refracting surfaces of equal radii of curvature and refractive index 1.5 face each other in air as shown in figure. A point object O is placed midway, between P and B. The separation between the images of O, formed by each refracting surface is:          [2025]

1 0.214 R  
2 0.114 R  
3 0.411 R  
4 0.124 R  

Ans.

(2)

For B

μ2VB–μ1u=μ2–μ1R

1.5VB+2R=0.5–R

1.5VB=–12R–2R

1.5VB=–52R ⇒ VB=–0.6R

For A

1.5VA+23R=0.5–R

1.5VA=–12R–23R

1.5VA=–76R ⇒ VA=–97R

Distance between images =2R–(0.6R+97R)=0.114R