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प्रश्न
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.
उत्तर
The sun is at infinity, so the convex lens forms its image at the second focal point, which is real and very much diminished in size.
While using the convex lens as burning glass, the rays of light from the sun (at infinity) are brought to focus on a piece of paper kept at the second focal plane of the lens. Due to the sufficient heat of the sun's rays, the paper burns. Hence, this lens is termed 'burning glass'.
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संबंधित प्रश्न
A lens forms an upright and diminished image of an object when the object is placed at its focal point. Name the lens and draw a ray diagram to show the image formation.
A lens forms an inverted image of an object. What is the nature of the image real or virtual?
An object is placed at a distance 5 cm from a convex lens of focal length 10 cm. The image formed is virtual, upright and _____.
For the object placed between the optical centre and focus of a convex lens, the image is ______.
Where should an object be placed so that a real and inverted image of the same size is obtained by a convex lens?
A small bulb is placed at the principal focus of a convex lens. When the bulb is switched on, the lens will produce
Draw ray diagrams showing the image formation by a convex lens when an object is placed
- between optical centre and focus of the lens
- between focus and twice the focal length of the lens
- at twice the focal length of the lens
- at infinity
- at the focus of the lens
A student focussed the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as under
Position of candle = 12.0 cm
Position of convex lens = 50.0 cm
Position of the screen = 88.0 cm
- What is the focal length of the convex lens?
- Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm?
- What will be the nature of the image formed if he further shifts the candle towards the lens?
- Draw a ray diagram to show the formation of the image in case (iii) as said above.
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 lens forms an upright and magnified image of an object. Draw a labelled ray diagram to show the image formation.
