A plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices ₁ and ₂ and R is the radius of curvature of the curved surface of t

Question

A plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices ₁ and ₂ and R is the radius of curvature of the curved surface of the lenses, then the focal length of the combination is

Quantrex Academy · Accepted Answer

Correct answer: C. R ( ₁- ₂ )

Focal length of the combination 1 f = 1 f₁ + 1 f₂ We have f₁= R ( ₁-1 ) and f₂= R ( ₂-1 ) or 1 f₁ = R ( ₁-1 ) or 1 f₂ =- R ( ₂-1 ) Putting these values in Eq. (i), we get aligned 1 f & = ( ₁-1 ) R - ( ₂-1 ) R & = [ ₁-1- ₂+1 ] R = ₁- ₂ R aligned

A plano-convex lens fits exactly into a plano-concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices ₁ and ₂ and R is the radius of curvature of the curved surface of the lenses, then the focal length of the combination is

Options

Correct answer

Step-by-step solution

More from Ray Optics