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

Two thin lenses have a combined power of $+9 \text{ D}$. When they are separated by a distance of $20 \text{ cm}$,their equivalent power becomes $+\frac{27}{5} \text{ D}$. The power of both the lenses in dioptre are respectively:

It is desired to make an achromatic combination of two lenses ($L_1$ and $L_2$) made of materials having dispersive powers $\omega_1$ and $\omega_2$ $(< \omega_1)$. If the combination of lenses is converging,then:

$A$ concave lens and a convex lens are arranged as shown in the figure. Find the position of the final image.

$A$ combination of two thin lenses in contact has a power of $+10 D$. The power reduces to $+6 D$ when the lenses are $0.25 m$ apart. The power of each individual lens is:

$A$ convex lens of focal length $30 \ cm$ is placed in contact with a concave lens of focal length $20 \ cm$. An object is placed at $20 \ cm$ to the left of this lens system. The distance of the image from the lens in $cm$ is . . . . . .

Vedclass Test Series

Exam Paper Generator

Online Exam Module