Objects and Images
Category : 10th Class
In this chapter we will use the term objects and image more often. Here the objects refers to the sources of light, which falls on the mirror and reflection takes places. It may be of two types, i.e. either very small or very large. The very small objects are called the point objects. The other term is the image which is obtained when the ray of light from an objects is reflected from a reflecting surface and an object like appearance is obtained. Image is of two types: real image and virtual image.
The real image are the images which can be obtained on the screen. For example the image which we see on the screen of the cinema hall is a real image. The image which cannot be obtained on the screen are called the virtual image. For example the image obtained from the reflection in the mirror are allvirtual image. It is just an illusion of which we can simply think of and which cannot be obtained in real sense. A plane mirror always forms the virtual image.
The image in the case of plane mirror is obtained only when we look into the mirror and cannot be obtained on the screen. It we place a screen behind the mirror it will not be possible for us to obtained the image of any object on the screen. The dotted line shown behind the mirror are only imaginary ray of lights.
There is no real ray of light behind the mirror as the surface of mirror is painted with silver paints, which do not allow the ray of light to pass through it. It is only the reflected light coming from the mirror, where the image is actually formed. Hence the image formed by the plane mirror is virtual and erect and size of the image is equal to the size of the object. The distance of the image is same as that of the object in front of the mirror.
All of us might have observed that when we stand in front of the mirror our left appears right and right appears left and vice versa. It seems that as if our images have been reversed. This reversal of image is called the lateral inversion. Hence, we can say that the image formed in the plane mirror is
In the above figure, we may observe that a tree which has been placed in front of a plane mirror he left side of the tree appears right and right side of the tree appears left. We can, therefore say that the image formed in the plane mirror is laterally inverted. The most common phenomena of lateral inversion which we observe is that the word AMBULANCE on the hospital van is written in the form of its mirror image as
This is because when we are driving a car and see the hospital van coming from behind in our rearer view mirror, we can read it as AMBULANCE and give side to the van as it carries the serious patient to the hospital.
The plane mirror can be used in barbershop, bathroom, jewelry shops, at the blind turns of some of the busy roads and in periscope.
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