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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.
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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 erect, magnified, and virtual image of an object. Draw a labelled ray diagram to show the image formation.
A converging lens forms the image of an object placed in front of it beyond 2F2 of the lens. Where is the object placed?
A converging lens forms the image of an object placed in front of it, beyond 2F2 of the lens. State three characteristics of the image.
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
An object of height 3cm is placed at 10cm from a concave lens of focal length 15cm. Find the size of the image.
Sudha finds out that the sharp image of the window pane of her science laboratory is formed at a distance of 15 cm from the lens. She now tries to focus the building visible to her outside the window instead of the window pane without disturbing the lens. In which direction will she move the screen to obtain a sharp image of the building? What is the approximate focal length of this lens?
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.
