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प्रश्न
Distinguish between:
Concave lens and Convex lens
State the differences between images formed by a convex and a concave lens.
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उत्तर
| Concave lens | Convex lens | |
| 1. | It is a diverging lens because it diverges the rays falling on it. | It is a converging lens because it converges the rays falling on it. |
| 2. | It is thin at the center and bulged at the edge. | It is thin at the edge and bulged at the centre. |
| 3. | The image formed by concave lens is always diminished and virtual. | The image formed by convex lens can be real as well as virtual. Also, the image formed can be diminished as well as magnified. |
| 4. | It has a virtual focus. | It has a real focus. |
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संबंधित प्रश्न
Where should an object be placed in order to use a convex lens as a magnifying glass?
What is a lens?
Describe with the help of a ray-diagram, the size, nature and position of the image formed by a convex lens when an object is placed beyond 2f in front of the lens.
An object 50 cm tall is placed on the principal axis of a convex lens. Its 20 cm tall image is formed on the screen placed at a distance of 10 cm from the lens. Calculate the focal length of the lens.
What kind of lens can form:
an erect magnified image?
Draw a diagram to represent the second focus of a convex lens.
Study the diagram given below.
- Name the lens LL’.
- What are the points O and O’ called?
- Complete the diagram to form the image of the object AB.
- State the three characteristics of the image.
- Name a device in which this action of lens is used.
Where is the image formed?
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?
In the following cases, where must an object be placed in front of a convex lens so that the image formed is upright and enlarged?
To find the image distance for varying object distances in case of a convex lens of focal length 15 cm, a student obtains on a screen a sharp image of a bright object by placing it at 20 cm distance from the lens. After that he gradually moves the object away from the lens and each time focuses the image on the screen.
(a) In which direction-towards or away from the lens does he move the screen to focus the object?
(b) How does the size of image change?
(c) Approximately at what distance does he obtain the image of magnification –1?
(d) How does the intensity of image change as the object moves farther and farther away from the lens?
An object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find (i) the position (ii) the magnification and (iii) the nature of the image formed.
Observe the following figure and answer the questions.
a) Which optical instrument shows arrangement of lenses as shown in the figure?
b) Write in brief the working of this optical instrument.
c) How can we get different magnifications in this optical instrument?
d) Draw the figure again and labelled it properly
Draw neat diagram to show the
Convergent action of a convex lens,
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 objective lens of photographic camera.
State the position of object, position of image, nature of image when: Convex lens is used as an erecting lens in terrestrial telescope.
How will you determine the focal length of a convex lens by the plane mirror method?
Write the name.
The lens used in simple microscope.
