Two similar thin equi-convex lenses,each of f | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(B) For two thin lenses in contact,the equivalent focal length $F_{1}$ is given by $\frac{1}{F_{1}} = \frac{1}{f} + \frac{1}{f} = \frac{2}{f}$,which i

Vedclass · Accepted Answer

$1:2$

Vedclass · Answer

(B) For two thin lenses in contact,the equivalent focal length $F_{1}$ is given by $\frac{1}{F_{1}} = \frac{1}{f} + \frac{1}{f} = \frac{2}{f}$,which implies $F_{1} = \frac{f}{2}$.When the space between the lenses is filled with a liquid of the same refractive index as the glass,the combination acts as a single block of glass. Since the outer surfaces are convex and the inner space is filled,the system effectively becomes a single convex lens with the same radii of curvature as the original lenses. However,the refractive index of the liquid is $\mu = 1.5$,which is equal to the glass. Thus,the entire system behaves as a single lens with focal length $F_{2} = f$.Therefore,the ratio $\frac{F_{1}}{F_{2}} = \frac{f/2}{f} = \frac{1}{2}$.

Similar Questions

$A$ beam of parallel rays is brought to a focus by a plano-convex lens. $A$ thin concave lens of the same focal length is joined to the first lens. The effect of this is:

$A$ convex lens of focal length $A$ and a concave lens of focal length $B$ are placed in contact with each other. The focal length of this combination is ......

Two thin lenses of focal lengths $f_1$ and $f_2$ are in contact. The focal length of this combination is

Two lenses of power $+5 \, D$ are placed at a distance $d$ to form sun goggles. The distance $d$ is . . . . . $cm$.

Obtain the equivalent focal length of a combination of thin lenses placed in contact.

Vedclass Test Series

Exam Paper Generator

Online Exam Module