A convex lens of focal length 30 cm and a co | vedclass

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

Question

(C) Let the focal length of the convex lens be $f_1 = +30 \ cm$ and the concave lens be $f_2 = -10 \ cm$.Let the distance between the two lenses be $d

Vedclass · Accepted Answer

$20$

Vedclass · Answer

(C) Let the focal length of the convex lens be $f_1 = +30 \ cm$ and the concave lens be $f_2 = -10 \ cm$.Let the distance between the two lenses be $d$.For a parallel beam of light to remain parallel after passing through the combination,the effective focal length $F$ of the system must be infinite $(F = \infty)$.The formula for the effective focal length of two lenses separated by a distance $d$ is given by:$\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2} - \frac{d}{f_1 f_2}$Substituting $F = \infty$,$f_1 = 30$,and $f_2 = -10$:$0 = \frac{1}{30} + \frac{1}{-10} - \frac{d}{(30)(-10)}$$0 = \frac{1}{30} - \frac{1}{10} + \frac{d}{300}$Multiplying by $300$:$0 = 10 - 30 + d$$d = 20 \ cm$.Thus,the distance between the two lenses is $20 \ cm$.

$A$ convex lens of focal length $30 \ cm$ and a concave lens of $10 \ cm$ focal length are placed so as to have the same axis. If a parallel beam of light falling on the convex lens leaves the concave lens as a parallel beam,then the distance between the two lenses will be.......$cm$.

Similar Questions

Two lenses having focal lengths in the ratio $f_1:f_2 = 2:3$ are combined to produce no net dispersion. Find the ratio of the dispersive powers of the glasses used.

$A$ convex lens of power $+6 D$ is placed in contact with a concave lens of power $-4 D$. What is the nature and focal length of the combination?

An object $AB$ is placed $15 \text{ cm}$ on the left of a convex lens $P$ of focal length $10 \text{ cm}$. Another convex lens $Q$ is now placed $15 \text{ cm}$ to the right of lens $P$. If the focal length of lens $Q$ is $15 \text{ cm}$, the final image is . . . . . . .

The focal length of the field lens (which is an achromatic combination of two lenses) of a telescope is $90 \ cm$. The dispersive powers of the two lenses in the combination are $0.024$ and $0.036$. The focal lengths of the two lenses are:

$A$ convex lens of focal length $40 \; cm$ is in contact with a concave lens of focal length $25 \; cm$. The power of the combination is:

Vedclass Test Series

Exam Paper Generator

Online Exam Module