Question

A lens has a power of -2.5 D. What is the focal length and nature of lens?

Solution

Given,
Power of lens, P = - 2.5 D

Therefore,

Focal length,

f = \frac{1}{P} = \frac{1}{- 2.5} m = - 40 cm .

The negative sign of focal length indicates that the lens is concave.

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Acids, Bases And Salts

A lens has a power of -2.5 D. What is the focal length and nature of lens?

Some More Questions From Acids, Bases and Salts Chapter

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.

What is lateral inversion of an image ? What is the cause of lateral inversion?

What is a spherical mirror? What are the two different types of spherical mirrors?

Define the following terms in connection with spherical mirrors:
(i) Pole (ii) Centre of curvature (iii) Radius of curvature (iv) Principal axis (v) Linear aperture (vi) Angular aperture (vii) Principle focus (viii) Focal length (ix) Focal plane.

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NCERT Sample Papers

Entrance Exams Preparation

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For Daily Free Study Material Join wiredfaculty

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Ncert Book Download

Acids, Bases And Salts

A lens has a power of -2.5 D. What is the focal length and nature of lens?

Some More Questions From Acids, Bases and Salts Chapter

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.

What is lateral inversion of an image ? What is the cause of lateral inversion?

What is a spherical mirror? What are the two different types of spherical mirrors?

Define the following terms in connection with spherical mirrors:(i) Pole (ii) Centre of curvature (iii) Radius of curvature (iv) Principal axis (v) Linear aperture (vi) Angular aperture (vii) Principle focus (viii) Focal length (ix) Focal plane.

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.

Define the following terms in connection with spherical mirrors:
(i) Pole (ii) Centre of curvature (iii) Radius of curvature (iv) Principal axis (v) Linear aperture (vi) Angular aperture (vii) Principle focus (viii) Focal length (ix) Focal plane.