As you have learnt already, such an image cannot be obtained on a screen. Since the reflected rays do not actually meet at I, but only appear to do so, we say that a virtual image of the point O is formed at I. For a viewer's eye at E, do the reflected rays appear to come from the point I. Do they meet now? If they meet, mark this point as I. How would you draw these rays? Call the reflected rays AB and CD, respectively. Then draw the reflected rays at the points A and C. Can you find out the direction of the reflected rays?ĭraw normals to the surface of the mirror PQ, at the points A and C. Let us understand a little more about the formation of image by a plane mirror in the following way:Ī source of light O is placed in front of a plane mirror PQ. Did the image appear at the same distance behind the mirror as the object was in front of it?.Paheli asked him to recall those features: You, too, can use the sun as the source of light.īhoojo remembered that he had studied in previous class, some features of the image of an object formed by a plane mirror. Paheli and Bhoojo performed the above activities outside the classroom with the sun as the source of light instead of a torch. It indicates that the incident ray, the normal at the point of incidence and the reflected ray all lie in the same plane. When you bend the paper you create a plane different from the plane in which the incident ray and the normal lie. The incident ray, the normal at the point of incidence and the reflected ray are all in this plane. When the whole sheet of paper is spread on the table, it represents one plane.
Bring the paper back to the original position. Bend that part of the projected portion on which the reflected ray falls.You will be able to see the reflected ray. Make sure that the reflected ray extends to the projected portion of the paper. Cut the projecting portion of the sheet in the middle. Let the sheet project a little beyond the edge of the Table. This time use a sheet of stiff paper or a chart paper. Let us perform another activity on reflection. If the experiment is carried out carefully, it is seen that the angle of incidence is always equal to the angle of reflection. There is a relation between the angle of incidence and the angle of reflection. Repeat the activity several times by changing the angle of incidence. Measure the angle of incidence and the angle of reflection. The angle between the normal and the reflected ray is known as the angle of reflection (∠r). The angle between the normal and incident ray is called the angle of incidence (∠i). This line is known as the normal to the reflecting surface at that point. Draw a line making an angle of 90º to the line representing the mirror at the point where the incident ray strikes the mirror. For simplicity, we use the term ray for a narrow beam of light.ĭraw lines showing the position of the plane mirror, the incident ray and the reflected ray on the paper with the help of your friends.
In reality, we have a narrow beam of light which is made up of several rays. The ray that comes back from the sur face after reflection is known as the reflected ray.Ī ray of light is an idealization. The light ray, which strikes any surface, is called the incident ray. Īfter striking the mirror, the ray of light is reflected in another direction. Place a strip of plane mirror in the path of the light ray. With slight adjustment of the torch and the comb you will see a ray of light along the paper on the other side of the comb. Throw light from a torch through the opening of the comb from one side. Hold the comb perpendicular to the sheet of paper. You can use a strip of black paper for this purpose. Take a comb and close all its openings except one in the middle. Laws of Reflectionįix a white sheet of paper on a drawing board or a table. Can you tell in which direction the light falling on a surface will be reflected? Let us find out. A mirror changes the direction of light that falls on it. The light may have been emitted by the object, or may have been reflected by it.Ī polished or a shiny surface can act as a mirror. It is only when light from an object enters our eyes that we see the object. But, can you see an object in the dark? It means that eyes alone cannot see any object. Have you ever thought how we see the various objects? You may say that eyes see the objects. You are able to see the words and sentences printed on this page. We also see clouds, rainbows and birds flying in the sky. Through it we see mountains, rivers, trees, plants, chairs, people and so many other things around us. The sense of sight is one of the most important senses. The world is largely known through the senses.
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