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प्रश्न
Point out the difference between a convex lens and a concave lens.
उत्तर
| Convex Lens | Concave Lens | ||
| 1. | It is thicker at the centre and thin at the ends. | 1. | It is thinner at the centre and thick at the ends. |
| 2. | It converges rays of light. | 2. | It diverges rays of light. |
| 3. | It has a real focus. | 3. | It has a virtual focus. |
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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.
If an object is at a considerable distance (or infinity) in front of a convex lens, where is the image formed?
Name one simple optical instrument in which the above arrangement of convex lens is used.
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.
The given below figure shows an object OA and its image IB formed by a lens
. 
draw suitable rays to locate the lens and its focus.
The image obtained while finding the focal length of convex lens is ....................
_______ times larger images can be obtained by using a simple microscope.
Simple microscope : Number of convex lens one : : compound microscope : _______
Find the odd one out and give its explanation.
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The above images are that of a specialized slide projector. Slides are small transparencies mounted in sturdy frames ideally suited to magnification and projection since they have a very high resolution and a high image quality. There is a tray where the slides are to be put into a particular orientation so that the viewers can see the enlarged erect images of the transparent slides. This means that the slides will have to be inserted upside down in the projector tray.
To show her students the images of insects that she investigated in the lab, Mrs. Iyer brought a slide projector. Her slide projector produced 500 times enlarged and inverted image of a slide on a screen 10 m away.
a. Based on the text and data given in the above paragraph, what kind of lens must the slide projector have?
b. If v is the symbol used for image distance and u for object distance then with one reason state what will be the sign for `"𝑣"/"𝑢"` in the given case?
c. A slide projector has a convex lens with a focal length of 20 cm. The slide is placed upside down 21 cm from the lens. How far away should the screen be placed from the slide projector’s lens so that the slide is in focus?
OR
c. When a slide is placed 15 cm behind the lens in the projector, an image is formed 3 m in front of the lens. If the focal length of the lens is 14 cm, draw a ray diagram to show image formation. (not to scale)
