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प्रश्न
State two differences between a convex and a concave lens.
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उत्तर १
| Convex lens | Concave lens | |
| 1. | A convex lens can form both real and virtual images | A concave lens always forms a virtual image |
| 2. | It can form a magnified image. | The image is always diminished in size. |
उत्तर २
1) A convex lens is thicker in the middle, while a concave lens is thinner in the middle.
2) A convex lens converges the light ray falling on it, while a concave lens diverges the light ray falling on it.
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संबंधित प्रश्न
The distance between principal focus and optical centre of the lens is _________.
- diameter
- focal length
- principal axis
- optical centre
Suppose you have focused on a screen the image of candle flame placed at the farthest end of the laboratory table using a convex lens. If your teacher suggests you to focus the parallel rays of the sun, reaching your laboratory table, on the same screen, what you are expected to do is to move the:
(a) lens slightly towards the screen
(b) lens slightly away from the screen
(c) lens slightly towards the sun
(d) lens and screen both towards the sun
Which type of lens forms always a virtual image?
A diverging mirror of radius of curvature 40 cm forms an image which is half the height of the object. Find the object and image positions.
Two lenses A and B have power of (i) +2D and (ii) −4D respectively. What is the nature and focal length of each lens?
If a spherical lens has a power of, −0.25 D, the focal length of this lens will be :
(a) −4 cm
(b) −400 mm
(c) −4 m
(d) −40 cm
If a spherical lens has a power of, −0.25 D, the focal length of this lens will be :
(a) −4 cm
(b) −400 mm
(c) −4 m
(d) −40 cm
My grandfather uses a bifocal lens in his spectacle. Explain why.
Complete the ray diagram to show how the rays pass into and out of the lens?
Complete the following table for convex lens:
| Sr. No. | Position of the object | Position of the image | Nature of the image |
| 1. | Beyond 2F1 | __________________ | ________________________ |
| 2. | __________________ | At infinity | ________________________ |
| 3. | __________________ | __________________ | Real, inverted and enlarged |
