Question

Two thin lenses of power + 3.5 D and - 2.5 D are placed in contact. Find the power and focal length of the lens combination.

Solution

Given,
Power of the lenses,
$P_{1} = + 3.5 D, P_{2} = - 2.5 D$

$∴$ Power of combination, $P = P_{1} + P_{2} = + 3.5 - 2.5 = + 1.0 D$

Thus, focal length of combination of lens, $f = \frac{1}{P} = \frac{1}{1.0 D} = 1.0 m .$

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Acids, Bases And Salts

Two thin lenses of power + 3.5 D and - 2.5 D are placed in contact. Find the power and focal length of the lens combination.

Some More Questions From Acids, Bases and Salts Chapter

Define a ray of light and a beam light. What are the different types of beams of light?

What is an optical medium? How can we classify different media on the basis of their behaviour towards light?

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.

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NCERT Sample Papers

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For Daily Free Study Material Join wiredfaculty

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Ncert Book Download

Acids, Bases And Salts

Two thin lenses of power + 3.5 D and - 2.5 D are placed in contact. Find the power and focal length of the lens combination.

Some More Questions From Acids, Bases and Salts Chapter

Define a ray of light and a beam light. What are the different types of beams of light?

What is an optical medium? How can we classify different media on the basis of their behaviour towards light?

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.

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.