Image formation by a convex mirror
Category : 10th Class
When the object is placed between P and F
When the object is placed in front of convex mirror, the image formed has following properties:
The Summary of the above Observation is given in the Table below:
S. NO. | Position of Object | Position of Image | Nature of Image | Size of Image |
1 | In front of Mirror | Behind Mirror and between P and F | Diminished | Virtual and Erect |
2. | At infinity | Behind the mirror and at F | Highly diminished | Virtual and Erect |
Uses of Concave Mirror
Uses of Convex Mirror
Sign Convention for Spherical Mirrors
Concave Mirror
Convex Mirror
Mirror Formula
The formula which gives the relation between the object distance (U), image distance (V) and focal length (F) is called the mirror formula. The distance between the pole and the object is called the object distance and is denoted by U. The distance between the pole and image is called the image distance and is denoted by V and the distance between the pole and focus is called focal length and is denoted by F. Hence the mirror formula is given by
\[\frac{\text{1}}{\text{Focal}\,\text{Length}}\text{=}\frac{\text{1}}{\text{Object}\,\text{Distance}}\text{+}\frac{\text{1}}{\text{Image}\,\text{Distance}}\,\,\frac{\text{1}}{\text{F}}\text{=}\frac{\text{1}}{\text{U}}\text{+}\frac{\text{1}}{\text{V}}\]
While finding one of the three value in the relation we must take care of sign convention of the mirror. Out of three parameter in the relation we can find any one of them provided two of them is given.
Magnification
It is defined as the extent to which an image can be enlarged or diminished by a mirror. For the spherical mirror the linear magnification is defined as the ratio of height of image to the height of object. If the magnification has positive sign then the image is virtual and erect. On the other hand, if the sign is negative
the image is real and inverted. The linear magnification is also defined as the ratio of image distance to the object distance. It is expressed as:
\[M=\frac{{{h}_{2}}}{{{h}_{1}}}=-\frac{V}{U}\]
Where,
\[{{h}_{1}}\]is the height of object,
\[{{h}_{2}}\]is the height of image,
U is the object distance
V is the image distance
What is the position of image when the object is placed at the infinity?
(a) Focus
(b) Between F and C
(c) At C
(d) Beyond C
(e) None of these
Answer: (a)
When an object is placed in front of the plane mirror the left appears right and the right appears left. This phenomenon is called
(a) Reflection
(b) Mirage
(c) Lateral Inversion
(d) Looming
(e) None of these
Answer: (C)
The point on the principal axis at which the ray of light converges after reflection is called
(a) Centre of Curvature
(b) Focus
(c) Pole
(d) Radii
(e) None of these
Answer: (b)
What is the nature of image when it is reflected from convex mirror?
(a) Real
(b) Inverted
(c) Highly Enlarged
(d) Virtual
(e) None of these
Answer: (d)
An object at 5 cm high forms an image at a distance of 6 cm and focal length of 15 cm. Find the position of image.
(a) 5cm
(b) 10cm
(c) 15cm
(d) 20cm
(e) None of these
Answer: (B)
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