Advertisements
Advertisements
प्रश्न
My grandfather uses a bifocal lens in his spectacle. Explain why.
Advertisements
उत्तर
Grandfather suffers from both myopia and hypermetropia. In few old age people near and distance vision is affected. In bifocal lens upper part is concave lens to correct myopia and lower part is convex lens for near vision. Hence grandfather uses bifocal lens in his spectacle.
APPEARS IN
संबंधित प्रश्न
The distance between principal focus and optical centre of the lens is _________.
- diameter
- focal length
- principal axis
- optical centre
Define focal length of a divergent lens.
A real image cannot be obtained on a screen.
State two differences between a convex and a concave lens.
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.
Explain why, a stick half immersed in water appears to be bent at the surface. Draw a labelled diagram to illustrate your answer.
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
What are the three principal rays that are drawn to construct the ray diagram for the image formed by a lens? Draw diagrams to support your answer.
A convex lens forms an image of an object equal to the size of the object. Where is the object placed in front of the lens?
A lens forms the image of an object placed at a distance 15 cm from it, at a distance 60 cm in front of it. Find the nature of image.
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 |
