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प्रश्न
The distance between an object and a convex lens is changing. It is noticed that the size of the image formed on a screen is decreasing. Is the object moving in a direction towards the lens or away from it?
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उत्तर
In the case of a convex lens, as the object moves away from it, the size of the image formed on a screen decreases.
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संबंधित प्रश्न
Analyse the following observation table showing variation of image distance (v) with object distance (u) in case of a convex lens and answer the questions that follow, without doing any calculations:
| S. No. | Object distance u(cm) | Image distance v(cm) |
| 1 | −90 | +18 |
| 2 | −60 | +20 |
| 3 | −30 | +30 |
| 4 | −20 | +60 |
| 5 | −18 | +90 |
| 6 | −10 | +100 |
(a) What is the focal length of the convex lens? Give reason in support of your answer.
(b) Write the serial number of that observation which is not correct. How did you arrive at this conclusion?
(c) Take an appropriate scale to draw ray diagram for the observation at S. No. 4 and find the approximate value of magnification.
Which type of mirror has:
positive focal length?
What would your image look like if you stood close to a large:
convex mirror?
How will you distinguish between a plane mirror, a concave mirror and a convex mirror without touching them?
- Draw a labelled ray diagram to show the formation of image in a convex mirror when the object is at infinity. Mark clearly the pole and focus of the mirror in the diagram.
- State three characteristics of the image formed in this case.
- Draw diagram to show how a convex mirror can be used to give a large field of view.
An arrow 2.5 cm high is placed at a distance of 25 cm from a diverging mirror of focal length 20 cm. Find the nature, position and size of the image formed.
Name two factors on which the focal length of a lens depends.
Explain why, a real image can be projected on a screen but a virtual image cannot.
A 5 cm tall object is placed perpendicular to the principle axis of a convex lens of focal length 12 cm. The distance of the object from the lens is 8 cm. Using the lens formula, find the position, size and nature of the image formed.
A full length image of a distant tall building can definitely be seen by using ______.
