Two similar plano-convex lenses are combined | vedclass

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

Question

(B) When two thin lenses with focal lengths $f_1$ and $f_2$ are placed in contact,the equivalent focal length $F$ is given by $\frac{1}{F} = \frac{1}{

Vedclass · Accepted Answer

$1:1:1$

Vedclass · Answer

(B) When two thin lenses with focal lengths $f_1$ and $f_2$ are placed in contact,the equivalent focal length $F$ is given by $\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2}$.In each of the three cases shown,we are combining two identical plano-convex lenses,each having a focal length $f$. For case $1$: The lenses are combined to form a biconvex lens. The power is $P = P_1 + P_2 = \frac{1}{f} + \frac{1}{f} = \frac{2}{f}$,so $F_1 = \frac{f}{2}$.For case $2$: The lenses are combined such that their curved surfaces face the same direction. The power is $P = P_1 + P_2 = \frac{1}{f} + \frac{1}{f} = \frac{2}{f}$,so $F_2 = \frac{f}{2}$.For case $3$: The lenses are combined such that their curved surfaces face each other. The power is $P = P_1 + P_2 = \frac{1}{f} + \frac{1}{f} = \frac{2}{f}$,so $F_3 = \frac{f}{2}$.Since $F_1 = F_2 = F_3$,the ratio of the focal lengths is $1:1:1$.

Two similar plano-convex lenses are combined together in three different ways as shown in the figure. The ratio of the focal lengths in the three cases will be

Similar Questions

Observe the following statements regarding the purification of bauxite:
$I$. During Hall's process,silica is removed as $Si$ (vapour).
$II$. Bauxite ore contaminated with $Fe_2O_3$ is purified in Baeyer's process.
$III$. During Serpeck's process,$AlN$ is formed.
The correct answer is:

Which of the following compounds has the highest boiling point?

The bob of a simple pendulum is hanging vertically down from a fixed identical bob by means of a string of length $l$. If both bobs are charged with a charge $q$ each,what is the time period of the pendulum? (Ignore the radii of the bobs.)

The solution of $\frac{dx}{dy} + \frac{x}{y} = x^2$ is:

$A$ horizontal tube of non-uniform cross-section has radii of $0.2\,m$ and $0.1\,m$ at points $P$ and $Q$ respectively. For streamline flow of an incompressible liquid, the rate of liquid flow is:

Vedclass Test Series

Exam Paper Generator

Online Exam Module