Focal length of a convex lens will be maximum | vedclass

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

Question

(C) According to the lens maker's formula,the focal length $f$ of a lens is given by:$\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \ri

Vedclass · Accepted Answer

red light

Vedclass · Answer

(C) According to the lens maker's formula,the focal length $f$ of a lens is given by:$\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$where $\mu$ is the refractive index of the lens material.From this,we can see that $\frac{1}{f} \propto (\mu - 1)$,which implies $f \propto \frac{1}{\mu - 1}$.According to Cauchy's dispersion formula,the refractive index $\mu$ is inversely proportional to the wavelength $\lambda$ of light $(\mu \propto \frac{1}{\lambda})$.As the wavelength $\lambda$ increases,the refractive index $\mu$ decreases.Since $f \propto \frac{1}{\mu - 1}$,a decrease in $\mu$ leads to an increase in the focal length $f$.Among the given colors,red light has the maximum wavelength $(\lambda_{red} > \lambda_{yellow} > \lambda_{green} > \lambda_{blue})$.Therefore,the refractive index $\mu$ is minimum for red light,which results in the maximum focal length for red light.

Focal length of a convex lens will be maximum for

Similar Questions

In the displacement method,we use a lens of focal length $f$ and the distance between the object and the screen is $60 \, cm$. $A$ possible value for the focal length is ........ $cm$.

The focal length of a thin converging lens in air is $20 \ cm$. When the lens is immersed in a liquid,it behaves like a concave lens of power $1 \ D$. If the refractive index of the material of the lens is $1.5$,the refractive index of the liquid is

An object is placed at a distance of $5 \, cm$ from the first principal focus of a convex lens of focal length $10 \, cm$. If a real image is formed,find its distance from the lens in $cm$.

The image of a small electric bulb fixed on the wall of a room is to be obtained on the opposite wall $3\;m$ away by means of a large convex lens. What is the maximum possible focal length (in $m$) of the lens required for the purpose?

Define power of a lens,obtain its equation and write its $SI$ unit.

Vedclass Test Series

Exam Paper Generator

Online Exam Module