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प्रश्न
Why does obtaining the image of the sun on paper with the help of a concave mirror burn the paper?
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उत्तर
The rays from the Sun are parallel. When these rays fall on the concave mirror, they converge to a single point on the focal plane of the mirror. Thus, a lot of heat is produced at that point. Now, if a paper is placed at that point to get the image of the Sun, the paper gets burnt because of the huge amount of heat concentrated at that point.
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संबंधित प्रश्न
List four characteristics of the images formed by plane mirrors.
A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be ______.
Three students A, B and C focussed a distant building on a screen with the help of a concave mirror. To determine focal length of the concave mirror they measured the distances as given below:
Student A : From mirror to the screen
Student B : From building to the screen
Student C : From building to the mirror
Who measured the focal length correctly ;
(a) Only A
(b) Only B
(c) A and B
(d) B and C
A ray of light is incident on a plane mirror making an angle of 90° with the mirror surface. The angle of reflection for this ray of light will be:
(a) 45°
(b) 90°
(c) 0°
(d) 60°
For what position of an object, a concave mirror forms a real image equal in size to the object?
With the help of a ray diagram, determine the position, nature and size of the image formed of an object placed at the centre of curvature of a concave mirror.
Make labelled ray diagrams to illustrate the formation of:
a virtual image by a converging mirror.
Mark clearly the pole, focus, centre of curvature and position of object in each case.
A student obtained a sharp image of the grills of a window on a screen using a concave mirror. His teacher remarked that for getting better results a well lit distant object (preferably the sun) should be focussed on the screen. What should be done for this purpose?
(A) Move the screen slightly away from the mirror
(B) Move the mirror slightly towards the screen
(C) Move the screen and the mirror away from the object
(D) Move the screen and the mirror towards the object
Give any two applications of a concave and convex mirror.
State whether true or false. If false, correct the statement.
When an object is at the centre of curvature of concave mirror the image formed will be virtual and erect.
Concave mirrors are used by dentists to examine teeth. Why?
Pick out the concave and convex mirrors from the following and tabulate them.
Rear-view mirror, Dentist’s mirror, Torchlight mirror, Mirrors in shopping malls, Make-up mirror.
A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is ______.
Under which of the following conditions a concave mirror can form an image larger than the actual object?
A concave mirror of radius 30 cm is placed in water. It’s focal length in air and water differ by ______.
The image formed by concave mirror is real, inverted and of the same size as that of the object. The position of object should be ______.
In torches, searchlights, and headlights of vehicles, the bulb is placed ______ of the concave mirror.
The focal length of a concave mirror is 5cm. Its radius of curvature is ______.
What is a concave and convex mirror?
Which type of mirror is used in the following?
Floodlights
