S.6 A' Level Physic 2 2017 Caltec S.6

1 SECTION A: OPTICS Light is a form of energy that travels in a straight line. Some objects produce light on their own and these are called luminous objects e.g sun, fire worms, fire fly . Most objects we see don’t produce light on their own but reflect it from luminous objects and these are called non-luminous objects e.g. moon, the stars, etc. Some objects do not allow light to go through them and these are called opaque objects e.g. wood, wall, people, etc. Some of them allow most of the light to go throu gh them and these are called transparent objects e.g. glass, clear water, clear polythene. Other objects allow some light to go through them and these are called translucent objects e.g. paper, bathroom glasses, tinted glass, etc. RAYS AND BEAMS A ray is the direction of the path taken by light. It is indicated by a straight line with an arrow on it. A beam is a collection of light rays. OR: A beam is a stream of light energy. Types of beams a) Parallel beam Rays are parallel to each other. This is obtained from light from a distant source and search lights. b) Convergent beam Rays from different directions meet at a common point. E.g. light behind a convex lens after p assing through it. c) Divergent beam Rays start from a common point and separate into different directions. E.g. light from a torch and car lights. REFLECTION OF LIGHT Reflection is the bouncing of light as it strikes a reflec ting surface. Types of reflection a) Regular reflection. Here, an incident parallel beam is reflected as a parallel beam when light falls on a smooth surface e.g. plane mirror, paper, clear water, highly polished surfaces. Incident beamReflected beam Reflecting surfacePlane b) Irregular (diffuse) …