Question

Two thin lenses are in contact and focal length of the combination is 80 cm. If the focal length of one lens is 20 cm, then what would be the power of the other lens?

Solution

Given,

Focal length of the combination of lens, f = 80 cm = 0.80 m

$Focal length, f_{1} = 20 cm = 0.20 m P_{2} = ?$

Power of the lens, $P = \frac{1}{f} = \frac{1}{0.80 m} = 1.25 D$

$P_{1} = \frac{1}{f_{1}} = \frac{1}{0.20 m} = 5 D$

Power of the combination o fthe lens, $P_{1} + P_{2} = P$

$∴$ $P_{2} = P - P_{1} = 1.25 - 5 = - 3.75 D .$

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Acids, Bases And Salts

Two thin lenses are in contact and focal length of the combination is 80 cm. If the focal length of one lens is 20 cm, then what would be the power of the other lens?

Some More Questions From Acids, Bases and Salts Chapter

What do you mean by reflection, refraction and absorption of light?

Which type of phenomenon (reflection or refraction) occurs when light falls on (i) a highly polished surface like a mirror and (ii) a transparent medium like glass or water?

What is meant by the optical image of an object?

What are real and virtual images? Can these images be obtained on a screen? Give reasons in support of your answer.

Give three points of differences between real and virtual images.

What is a mirror? Mention the different types of mirrors commonly used.

Define the following terms in connection with reflection of light:
Incident ray, reflected ray, point of incidence, normal, angle of incidence and angle of reflection.

State the laws of reflection of light.

Are the laws of reflection applicable to plane surfaces also valid for curved surfaces?

State the important properties of images formed by plane mirrors.

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

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For Daily Free Study Material Join wiredfaculty

WhatsApp Group

Download Android App

Ncert Book Download

Acids, Bases And Salts

Two thin lenses are in contact and focal length of the combination is 80 cm. If the focal length of one lens is 20 cm, then what would be the power of the other lens?

Some More Questions From Acids, Bases and Salts Chapter

What do you mean by reflection, refraction and absorption of light?

Which type of phenomenon (reflection or refraction) occurs when light falls on (i) a highly polished surface like a mirror and (ii) a transparent medium like glass or water?

What is meant by the optical image of an object?

What are real and virtual images? Can these images be obtained on a screen? Give reasons in support of your answer.

Give three points of differences between real and virtual images.

What is a mirror? Mention the different types of mirrors commonly used.

Define the following terms in connection with reflection of light:Incident ray, reflected ray, point of incidence, normal, angle of incidence and angle of reflection.

State the laws of reflection of light.

Are the laws of reflection applicable to plane surfaces also valid for curved surfaces?

State the important properties of images formed by plane mirrors.

Mock Test Series

NCERT Sample Papers

Entrance Exams Preparation

Define the following terms in connection with reflection of light:
Incident ray, reflected ray, point of incidence, normal, angle of incidence and angle of reflection.