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प्रश्न
What type of lens would you use as a magnifying glass? How close must the object be to the lens?
उत्तर
For a magnifying glass, we use a convex lens. The object should be placed between the optical centre and the focus.
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संबंधित प्रश्न
An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagram and find the position, size and the nature of the image formed.
A convex lens of focal length 0.10 m is used to form a magnified image of an object of height 5 mm placed at a distance of 0.08 m from the lens. Calculate the position, nature and size of the image.
An object 3 cm high is placed 24 cm away from a convex lens of focal length 8 cm. Find by calculations, the position, height and nature of the image.
Complete the following sentence.
A long-sighted person cannot see ........... objects clearly. Long-sightedness can be corrected by using .............. lenses.
In a certain murder investigation, it was important to discover whether the victim was long-sighted or short-sighted. How could a detective decide by examining his spectacles?
The given below figure shows an object OA and its image IB formed by a lens. State three characteristics of the image.
In the following cases, where must an object be placed in front of a convex lens so that the image formed is inverted and enlarged?
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 | –60 | +12 |
| 2 | –30 | +15 |
| 3 | –20 | +20 |
| 4 | –15 | +30 |
| 5 | –12 | +60 |
| 6 | –9 | +90 |
(a) What is the focal length of the convex lens? State reason for your answer.
(b) For what object-distance (u) is the corresponding image-distance (v) not correct? How did you arrive at this conclusion?
(c) Choose an appropriate scale to draw a ray diagram for the observation at S. No. 4 and find the approximate value of magnification.
State the position of object, position of image, nature of image when: Convex lens is used as objective lens of photographic camera.
Distinguish between:
Concave lens and Convex Lens
