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Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 10
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Syllabus

Images Formed by Convex Lenses

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Topics

  • Rules for Image Formation by a Convex Lens
  • Experiment
  • Images formed by convex lenses for different positions of the object

Rules for Image Formation by a Convex Lens

Rule No. Description Diagram
Rule 1 When the incident ray is parallel to the principal axis, the refracted ray passes through the principal focus (F₂).
Rule 2 When the incident ray passes through the principal focus (F₁), the refracted ray becomes parallel to the principal axis.
Rule 3 When the incident ray passes through the optical centre (O) of the lens, it does not change direction.

Experiment

1. Aim: To study the formation of images by a convex lens at different object positions and observe the nature, size, and position of the image.

2. Requirements: convex lens, screen, meter scale, lens stand, candle, and chalk

3. Procedure

  • Draw a straight line on a table and place the convex lens at the centre (O).
  • Place a screen on one side and adjust it to form a clear image of a distant object, marking its focus (F₁).
  • Measure the distance O to F₁ and mark 2F₁ at twice this distance. Repeat for F₂ and 2F₂ on the other side.
  • Place a burning candle beyond 2F₁ and adjust the screen to obtain a clear image. Record its position, size, and nature.
  • Repeat the experiment by placing the candle at different positions: beyond 2F₁, at 2F₁, between 2F₁ and F₁, at F₁, and between F₁ and O.
  • Observe and record the image characteristics for each case.

4. Conclusion

  • When the object is placed beyond 2F₁, the image is between F₂ and 2F₂, real, inverted, and smaller.
  • If placed at 2F₁, the image is same-sized, real, and inverted at 2F₂.
  • When placed between 2F₁ and F₁, the image is beyond 2F₂, real, inverted, and magnified.
  • At F₁, the image is at infinity, highly magnified, real, and inverted.
  • If placed between F₁ and O, the image is virtual, erect, and magnified on the same side as the object.

Images formed by convex lenses for different positions of the object

S. No. Position of the Object Position of the Image Size of the Image Nature of the Image Ray Diagram
1 At infinity At focus F₂ Point image Real and inverted
2 Beyond 2F₁ Between F₂ and 2F₂ Smaller Real and inverted
3 At 2F₁ At 2F₂ Same size Real and inverted
4 Between F₁ and 2F₁ Beyond 2F₂ Larger Real and inverted
5 At focus F₁ At infinity Very large Real and inverted
6 Between F₁ and O On the same side of the lens as the object Very large Virtual and erect

 

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Related QuestionsVIEW ALL [22]

An object is placed at a distance of more than 40 cm from a convex lens of focal length 20 cm. The image formed is real, inverted and ______.

Which of the following lens would you prefer to use while reading small letters found in a dictionary?

Complete the following table based on image formation by convex lens:

Position of Object Position of Image Nature of Image
At infinity (a) ______ Real and inverted and highly diminished image
Beyond 2F1 (b) ______ (c) ______
At 2F1 (d) ______ Real, inverted, same size (as object) image
Between F1 and 2F1 Beyond 2F2 (e) ______
At focus F1 (f) ______ Real, inverted and highly enlarged image

A small bulb is placed at the principal focus of a convex lens. When the bulb is switched on, the lens will produce

Draw a ray diagram to show how a converging lens can form an image of the sun. Hence give a reason for the term ‘burning glass’ for a converging lens used in this manner.

A lens forms an upright and magnified image of an object. Draw a labelled ray diagram to show the image formation.

An object is placed at a distance 20cm from a convex lens of focal length 10cm. Find the image distance and nature of the image.

Explain the rules for obtaining images formed by a convex lens with the help of ray diagram.

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