An achromatic convergent lens of focal length $20 \, cm$ is made of two lenses (in contact) of materials having dispersive powers in the ratio of $1 : 2$ and having focal lengths $f_1$ and $f_2$. Which of the following is true?
- A$f_1 = 10 \, cm, f_2 = -20 \, cm$
- B$f_1 = 20 \, cm, f_2 = 10 \, cm$
- C$f_1 = -10 \, cm, f_2 = -20 \, cm$
- D$f_1 = 20 \, cm, f_2 = -20 \, cm$
Explore More
Similar Questions
Concave and convex lenses are placed touching each other. The ratio of the magnitudes of their power is $2:3$. The focal length of the system is $30 \ cm$. Then the focal lengths of the individual lenses are:
Difficult
View SolutionTwo identical thin biconvex lenses of focal length $15 \, cm$ and refractive index $1.5$ are in contact with each other. The space between the lenses is filled with a liquid of refractive index $1.25$. The focal length of the combination is $cm$.
DifficultJEE MAIN 2022
View Solution$A$ lens of power $+2$ diopters is placed in contact with a lens of power $-1$ diopter. The combination will behave like
Medium
View SolutionThe focal length (in $cm$) of a lens with dispersive power $0.45$ that should be placed in contact with a convex lens of focal length $84 \,cm$ and dispersive power $0.21$ to form an achromatic combination is:
$A$ convex lens of focal length $20 \, cm$ is cut into two equal parts. This results in two plano-convex lenses as shown in the figure. These two parts are then placed in contact with each other as shown in the figure. What will be the focal length of the system in $cm$?
Easy
View SolutionVedclass Products
For Students
Vedclass Test Series
Mock tests in real JEE/NEET style with performance analysis. 5-day free trial.
Start Free TrialFor Teachers
Exam Paper Generator
Generate Set A/B/C/D exam papers from 7.5L+ questions in 2 minutes. 3 chapters free.
Try FreeFor Institutes
Online Exam Module
Live online exams with unlimited students, 360° analytics & white-label branding.
See Demo