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प्रश्न
Observe the given figure and answer the following questions.
- Where is the above type of lens construction used?
- What type of image is formed by an objective lens?
- What happens instead of placing at Fo if the object is placed in between O and Fo?
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उत्तर
- The above type of lens construction is used in a compound microscope.
- The image formed by the objective is real, inverted, and formed at a distance within the focal length of the eyepiece.
- If the object is placed in between O and Fo, a virtual image will be formed on the same side of the objective as that of the object. As a result, compound microscope will not be able to operate as expected.
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संबंधित प्रश्न
(a) Draw a ray diagram to show the formation of image by a concave lens when an object is placed in front of it.
(b) In the above diagram mark the object distance (u) and the image distance (v) with their proper signs (+ve or –ve as per the new Cartesian sign convention) and state how these distances are related to the focal length (f) of the concave lens in the case.
(c) Find the nature and power of a lens which forms a real and inverted image of magnification –1 at a distance of 40 cm from the optical centre.
A beam of light travelling in air is incident of water. Draw a ray-diagram indicating the change in its path in water.
If an object is placed at the focus of a convex lens, where is the image formed?
If an object is at a considerable distance (or infinity) in front of a convex lens, where is the image formed?
Describe the nature of image formed when an object is placed at a distance of 30 cm from a convex lens of focal length 15 cm.
How would a pencil look like if you saw it through a convex lens? (Assume the pencil is close to the lens). Is the image real or virtual?
A beam of parallel light rays is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the diagram below:
Which of the following could be inside the box?
An object is placed 20 cm from (a) a converging lens, and (b) a diverging lens, of focal length 15 cm. Calculate the image position and magnification in each case.
What would be the diameter of the image of the flower on the film?
The focal lengths of four convex lenses P, Q, R and S are 20 cm, 15 cm, 5 cm and 10 cm, respectively. The lens having the greatest power is:
Study the diagram below.
what are the points O, O’ called?
A lens forms an upright and magnified image of an object State whether the image is real or virtual
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.
Distinguish between:
Concave lens and Convex lens
Where must a point source of light be placed in front of a convex lens so as to obtain a parallel beam of light?
State two applications of a convex lens.
If an object is placed in front of a convex lens beyond 2F1, then what will be the position, relative size, and nature of an image which is formed? Explain with a ray diagram.
Write the name.
The lens used in simple microscope.
A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this a correct statement? If yes, where shall the object be placed in each case for obtaining these images?
Distinguish between Concave lens and Convex lens.
