Advertisements
Advertisements
प्रश्न
The size of image of an object by a convex lens of focal length 20 cm is observed to be reduced to `1/3` rd of its size . Find the distance of the object from the optical centre of the lens .
Advertisements
उत्तर
Given :
`f = 20 "cm" ; ν = 1/3 u "cm" ; u = ?`
we know that ,
`1/f = 1/ν + 1/u`
using sign convensions ,
`1/f = -1/u - 1/ν `
`therefore 1/20 = -1/u - 3/4 = -4/u`
`therefore u = -4 xx 20 = -80 "cm"`
`therefore u = -80 "cm"`
APPEARS IN
संबंधित प्रश्न
| Column I | Column II | Column III | |
| 1 | Dispersion | Long-sightedness | Twinkling of stars |
| 2 | Refraction | Splitting of white light into component colours | Convex lens |
| 3 | Hypermetropia | Change in the direction of the ray of light due to change in medium | Spectrum of seven colours |
With the help of a labelled ray-diagram, describe how a plane mirror forms an image of a point source of light placed in front of it. State the characteristics of the image formed in a plane mirror.
Fill in the following blank with suitable word:
Light bends when is passes from water into air. We say that it is ............
A vertical ray of light strikes the horizontal surface of some water:
What is the angle of refraction?
Water is optically .......... than air.
Due to _______ pencil looks bent in water, in the given experiment.
Write scientific reason.
The coin disappears in a vessel as it is seen from a specific location. But as soon as the water is poured into the vessel to a certain level, the coin appears.
If a beam of red light and a beam of violet light are incident at the same angle on the inclined surface of a prism from air medium and produce angles of refraction r and v respectively, which of the following is correct?
The angle of incidence from air to glass at the point O on the hemispherical glass slab is.
Which object use the reflection of light?
