(A) To form an achromatic doublet,we combine a convex lens of crown glass with a concave lens of flint glass.The condition for achromatism is $\frac{\

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Convergent of crown and divergent of flint

(A) To form an achromatic doublet,we combine a convex lens of crown glass with a concave lens of flint glass.The condition for achromatism is $\frac{\omega_1}{f_1} + \frac{\omega_2}{f_2} = 0$,where $\omega$ is the dispersive power and $f$ is the focal length.Since crown glass has lower dispersive power $(\omega_c Thus,the correct combination is a convergent lens of crown glass and a divergent lens of flint glass.

Class 12 Physics Ray Optics and Optical Instruments Refraction by Lenses

Easy

An achromatic telescope objective is to be made by combining the lenses of flint and crown glasses. This proper choice is

A
Convergent of crown and divergent of flint
B
Divergent of crown and convergent of flint
C
Both divergent
D
Both convergent

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Class 12 Questions

Class 12

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Ray Optics and Optical Instruments

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Refraction by Lenses

If the radius of curvature of the convex surface of a plano-convex lens is $10 \ cm$ and its focal length is $30 \ cm$,what is the refractive index of the material of the lens?

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$A$ beam of light converges at a point $P$. Now a lens is placed in the path of the convergent beam $12 \, cm$ from $P$. At what point does the beam converge if the lens is a concave lens of focal length $16 \, cm$ (in $, cm$)?

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Two point light sources are $24 \, cm$ apart. Where should a convex lens of focal length $9 \, cm$ be placed between them from one source so that the images of both the sources are formed at the same place (in $, cm$)?

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$A$ plano-convex lens has a diameter of $6\, cm$ and a thickness of $3\, mm$ at the center. If the speed of light in the material of the lens is $2 \times 10^{8}\, m/s$,then the focal length of the lens is ..... $cm$.

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$A$ magnifying lens has a focal length of $10 \, cm$. If the image is formed at a distance of $30 \, cm$ from the lens,what is the magnification?

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An achromatic telescope objective is to be made by combining the lenses of flint and crown glasses. This proper choice is

Similar Questions

If the radius of curvature of the convex surface of a plano-convex lens is $10 \ cm$ and its focal length is $30 \ cm$,what is the refractive index of the material of the lens?

$A$ beam of light converges at a point $P$. Now a lens is placed in the path of the convergent beam $12 \, cm$ from $P$. At what point does the beam converge if the lens is a concave lens of focal length $16 \, cm$ (in $, cm$)?

Two point light sources are $24 \, cm$ apart. Where should a convex lens of focal length $9 \, cm$ be placed between them from one source so that the images of both the sources are formed at the same place (in $, cm$)?

$A$ plano-convex lens has a diameter of $6\, cm$ and a thickness of $3\, mm$ at the center. If the speed of light in the material of the lens is $2 \times 10^{8}\, m/s$,then the focal length of the lens is ..... $cm$.

$A$ magnifying lens has a focal length of $10 \, cm$. If the image is formed at a distance of $30 \, cm$ from the lens,what is the magnification?

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