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प्रश्न
The image obtained while finding the focal length of convex lens is ....................
विकल्प
a) a real and erect.
b) virtual and erect.
c) real and inverted.
d) virtual and inverted.
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उत्तर
c) real and inverted.
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संबंधित प्रश्न
To find the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen.
(a) In which direction – towards or away from the lens, does he move the screen to focus the object?
(b) What happens to the size of image – does it increase or decrease?
(c) What happen when he moves the object very close to the lens?
A beam of light travelling in air is incident of water. Draw a ray-diagram indicating the change in its path in water.
Draw a labelled ray diagram to show how a ray of light is refracted when it passes:
from air into an optically denser medium.
Where should an object be placed in front of a convex lens so as to obtain its real, inverted and magnified image?
What is a lens?
Describe with the help of a ray-diagram, the formation of image of a finite object placed in front of convex lens between f and 2f. Give two characteristics of the image so formed.
A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.
- Rewrite the image distances in the correct order.
- What would be the image distance if the object distance was 90 cm?
- Which of the object distances gives the biggest image?
- What is the focal length of this lens?
A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.
Which of the object distances gives the biggest image?
An image formed on a screen is three times the size of the object. The object and screen are 80 cm apart when the image is sharply focussed.
- State which type of lens is used.
- Calculate focal length of the lens.
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:
A parallel oblique beam of light falls on a convex lens. Draw a diagram to show the refraction of light through the lens.
A lens forms an upright and magnified image of an object. Name the lens.
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?
A convex lens has a divergent action and a concave lens has a convergent action.
If you are to determine to focal length of a convex lens, you should have
(A) a convex lens and a screen
(B) a convex lens and a lens holder
(C) a lens holder, a screen holder and a scale
(D) a convex lens, a screen, holder for them and a scale
Where should an object be placed in front of a convex lens to get a real image of the size of the object?
What is the difference between a double convex and a bi-convex lens?
State the position of object, position of image, nature of image when: Convex lens is used as an erecting lens in terrestrial telescope.
Find the odd one out and give its explanation.
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?
