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REFLECTION OF LIGHT The phenomenon of bouncing off the light in the same medium, when it falls on a polished or shiny surface, is called reflection of light. Example: A mirror, polished surface of metal, etc., reflects (or bounces off) most of the light falling or incident on it, as shown in figure 1.2. Where, i = Incident angle, PO = Incident ray, MN= Plane mirror, ON = Normal, r = Angle of reflection, 0Q= Reflected ray, o = Incident point. Laws of Reflection of Light (a) Angle of incidence (i) is always equal to angle of reflection (r). angle i = angle r, and (b) Incident ray, reflected ray and normal to the mirror at the point of incidence all the three lie in the same plane. These two laws of reflection of light are applicable for all kind of mirrors such as spherical mirror, plane mirror, curved mirror.

LIGHT Light is a kind of energy, which travels in the form of electromagnetic waves and produces sensation in our eyes. An object reflects light incident on it and this reflected light received by our eyes, makes us able to see the things around us. "In this way things are classified in two ways on the basis of reflection of light." (i) Luminous bodies: Those bodies which produce light, are called luminous bodies, e.g., electric bulb, sun, etc. (ii) Non-luminous bodies: Those bodies which cannot produce light, are called non-luminous bodies, e.g., book, chair, moon, etc. Non-luminous bodies when comes in contact of luminous bodies, becomes visible due to radiations incident on them. "On the basis of medium of propagation of light bodies are classified as follows:" (i) Opaque bodies: Those bodies which do not allow light to pass through them are called opaque bodies, e.g., wall, wood, book,...

ADVANCED SUNRISE AND DELAYED SUNSET The sun is visible to us about 2 minutes before the actual sunrise and about 2 minutes after the actual sunset because of atmospheric refraction. Actual sunrise means actual crossing of the horizon by the sun. In the figure 2.14 this situation is shown. It shows the actual and apparent positions of the sun with respect to the horizon. So the difference between actual sunset and apparent sunset is about 2 minutes. The apparent flattening of the sun's disc at sunrise and sunset is also due to the same phenomenon.

HUMAN EYE Human eye is one of the most valuable and sensitive sense organs. Human eye enables us to see the wonderful world and colours around us by using light. Our eye is like a photo camera which has a natural lens inbuilt. This lens is made up of transparent material medium. Thus human eye is one of the most significant sense organs as it enables us to see the beautiful colourful world around us. The structure of human eye's different parts and their description is as follows.

➤ Aperture Here we'll discuss only those spherical mirrors which are of small aperture i.e., we have to study only those of spherical mirrors which are of small aperture in our syllabus. The circular diameter of reflecting face of a mirror is called aperture. In figures 1.8 (a) and 1.8 (b), MN is denoted by aperture. It is normal to principal axis.

ELECTROMAGNETIC INDUCTION- The phenomenon of production of electromotive force (emf) at the ends of a conductor when it is placed in a changing magnetic field is called electromagnetic induction. The magnitude of electromotive force is given by Faraday's law of induction. In 1831, Faraday discovered the electromagnetic induction. In this experiment, Faraday stated that how a moving magnet can be used to produce electric current.