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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
Consider the following diagram in which M is a mirror and P is an object and Q is its magnified image formed by the mirror.
State the type of the mirror M and one characteristic property of the image Q.
The radius of curvature of a spherical mirror is 20 cm. What is its focal length?
The image formed by a concave mirror is observed to be virtual, erect and larger than the object. Where should be the position of the object?
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 3 cm tall object is placed 18 cm in front of a concave mirror of focal length 12 cm. At what distance from the mirror should a screen be placed to see a sharp image of the object on the screen. Also calculate the height of the image formed.
Draw the following diagram in your answer book and show the formation of image with the help of suitable rays:
An object is placed at the following distances from a concave mirror of focal length 15 cm, turn by turn:
(a) 35 cm
(b) 30 cm
(c) 20 cm
(d) 10 cm
Which position of the object will produce:
(i) a magnified real image?
(ii) a magnified virtual image?
(iii) a diminished real image?
(iv) an image of same size as the object?
Giving reasons, state the 'signs' (positive or negative) which can be given to the following:
(a) object distance (u) for a concave mirror or convex mirror
(b) image distance (v) for a concave mirror
(c) image distance (v) for a convex mirror
What is the position of the image when an object is placed at a distance of 20 cm from a concave mirror of focal length 20 cm?
If an object of 10 cm height is placed at a distance of 36 cm from a concave mirror of focal length 12 cm, find the position, nature and height of the image.
A concave mirror has a focal length of 4 cm and an object 2 cm tall is placed 9 cm away from it. Find the nature, position and size of the image formed.
Which of the following are concave mirrors and which convex mirrors?
Why does a beam of light when it enters glass at an angle? Why does it not bend if it inters the glass at right angles?
Draw a ray diagram to show the formation of image of an object placed at the centre of curvature of a concave mirror. State the position, size and nature of the image.
Match the following.
| Convex mirror | Radio telescopes |
| Parobolic mirror | Rear – view mirror |
| Snell’s law | Kaleidoscope |
| Dispersion of light | sin i/sin r =μ |
| Refractive index | Rainbow |
Give any two applications of a concave and convex mirror.
While looking at the above diagram, Nalini concluded the following.
- the image of the object will be a virtual one.
- the reflected ray will travel along the same path as the incident ray but in opposite direction.
- the image of the object will be inverted.
- this is a concave mirror and hence the focal length will be negative.
Which one of the above statements are correct?
You are provided with a convex mirror, a concave mirror, a convex lens and a concave lens. You can get an inverted image from
In the headlights of motor vehicles, ______ mirrors are used as reflectors.
______ mirrors make things look larger when objects are placed close to them.
