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प्रश्न
State two uses of a concave mirror.
Give the uses of a concave mirror.
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उत्तर १
Two uses of concave mirror:
(i) It is used as a shaving mirror.
(ii) It is used as reflector in torch, head light of automobiles etc.
उत्तर २
The uses of a concave mirror are
(i) In torches and headlights: The source of light is placed at the focus to obtain a parallel beam of light.
(ii) In floodlights: The source of light is placed just beyond the center of curvature so as to get an intense beam of light.
(iii) Reflecting mirrors for projector lamps: The object is placed at the center of curvature to obtain an image of the same size.
- To collect heat radiations in solar devices: Heat radiations from the sum coming from infinity are brought to focus by a concave mirror in its focal plane.
- Shaving mirror, dentist’s mirror: It produces an erect virtual and highly magnified image of an object placed between its pole and focus.
vi. Solar furnaces: Large concave mirrors are used to concentrate sunlight to produce heat in a solar furnace.
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संबंधित प्रश्न
A student obtains a sharp image of the distant window (W) of the school laboratory on the screen (S) using the given concave mirror (M) to determine its focal length. Which of the following distances should he measure to get the focal length of the mirror?
Name the spherical mirror which has:
(a) virtual principal focus.
(b) real principal focus.
When a spherical mirror is held towards the sun and its sharp image is formed on a piece of carbon paper for some time, a hole is burnt in the carbon paper.
- What is the nature of spherical mirror?
- Why is a hole burnt in the carbon paper?
- At which point of the spherical mirror the carbon paper is placed?
- What name is given to the distance between spherical mirror and carbon paper?
- What is the advantage of using a carbon paper rather than a white paper?
The diverging lens in part (a) is replaced by a converging lens also of focal length 100 mm. The object remains in the same position and an image is formed by the converging lens. Compare two properties of this image with those of the image formed by the diverging lens in part (a).
How is a spherical mirror used to diverge a beam of light from a point? Name the type of mirror used.
Explain the following term:
Incident ray
Draw diagram/diagrams to show them.
Name the kind of mirror used to obtain:
A real and diminished image.
Which mirror will you prefer to use as a rear view mirror in a car : plane mirror or convex mirror? Give one reason.
The focal length of a concave mirror is 10 cm. Find its radius of curvature.
The image formed by a convex mirror is of size one third the size of object. How are u and v related?
A concave mirror forms a virtual image of size twice that of the object placed at a distance 5 cm from it. Find:
- the focal length of the mirror
- position of image
When an object of height 1 cm is kept at a distance 4 cm from a concave mirror, its erect image of height 1.5 cm is formed at a distance 6 cm behind the mirror. Find the focal length of mirror, by drawing.
An object 5 cm high is placed at a distance 60 cm in front of a concave mirror of focal length 10 cm. Find the position and size of the image.
The sun is seen before the sunrise and after the sunset.
Draw a ray diagram to show the formation of the image, when the object is placed between optical centre and principal focus of a convex lens.
State the signs and values of magnifications in the above mentioned case.
An object 5 cm high forms a virtual image of 1.25 cm high, when placed in front of a convex mirror at a distance of 24 cm. Calculate:
- the position of the image
- the focal length of the convex mirror.
Define the following term:
concave mirror
Define the following term in relation to concave mirror.
Focal length
The diagram below shows the parallel rays incident on a convex mirror. C is the centre of the curvature of the mirror. By drawing the paths of the reflected rays, label the focus F and hence find the focal length of the mirror.
The distance from the pole to the focus is called ______.
Define focal length.
A student traces the path of a ray of light passing through a rectangular slab.
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For measuring the angle of incidence, he must position the protractor in the manner shown in the figure:
The minimum length of the mirror required to see the full image of the person is half ‘ of his height.
