मराठी
Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 10
पाठ्यपुस्तक उत्तरे८४४३
संकल्पना स्पष्टीकरण आणि व्हिडिओ३२८
अभ्यासक्रम

Concave Lens

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Topics

  • Introduction
  • Applications
Maharashtra State Board: Class 10

Introduction

A concave lens is a type of lens that diverges light rays, spreading them outward. It is made by joining two spherical surfaces, where the lens is thin at the centre and thick at the edges. Due to its diverging property, it is also called a diverging lens.

When parallel rays of light pass through a concave lens, they spread out (diverge) away from a common point. This results in the formation of a virtual, upright, and diminished image. Because of this property, concave lenses are widely used in correcting myopia (nearsightedness) by making distant objects appear smaller and clearer.

A concave lens may be of the following three kinds:

  1. Bi-concave or double-concave or equi-concave,
  2. Piano-concave, and
  3. Convexo-concave. 

Maharashtra State Board: Class 10

Applications:

1. Optical Instruments

  • Telescope & Binoculars: Used to correct distortions and improve focus.
  • Microscopes & Cameras: Enhances image quality by reducing aberrations.

2. Vision Correction

  • Eyeglasses for Myopia: Helps nearsighted people see distant objects clearly by diverging light rays before they reach the retina.

3. Security Devices

  • Peepholes in Doors: Provides a wide-angle view by minimising object proportions.

4. Light and Laser-Based Devices

  • Medical Equipment & Scanners: Used in laser-based devices for precise functioning.
  • CD Players: Helps in focusing laser beams for reading discs.
  • Torchlights: Spread light widely from a small bulb.

Related QuestionsVIEW ALL [116]

An object is placed at a distance of 60 cm from a concave lens of focal length 30 cm.
(i) Use the lens formula to find the distance of the image from the lens.
(ii) List four characteristics of the image (nature, position, size, erect/inverted) formed by the lens in this case.
(iii) Draw a ray diagram to justify your answer of the part (ii).

 Where must the object be placed for the image formed by a converging lens to be: 

 virtual, upright and larger than the object?

At what distance from a concave lens of focal length 20 cm a 6 cm tall object be placed so as to obtain its image at 15 cm from the lens? Also calculate the size of the image formed.
Draw a ray diagram to justify your answer  for the above situation and label it.

Copy and complete the diagram below to show what happens to the rays of light when they pass through the concave lens:

Where must the object be placed for the image formed by a converging lens to be: 

 real, inverted and smaller than the object?

An object 60 cm from a lens gives a virtual image at a distance of 20 cm in front of the lens. What is the focal length of the lens? Is the lens converging or diverging? Give reasons for your answer.

 How would you alter the above diagram to show how a converging lens can produce a beam of parallel rays of light. 

Where must the object be placed for the image formed by a converging lens to be: 

 real, inverted and larger than the object? 

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