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Lesson_4.6_Printable_PPT

# Lesson_4.6_Printable_PPT - Properties of Light The present...

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Properties of Light The present day understanding of light is that it is made up of tiny particles called photons which have wavelength and frequency. The energy E of a photon is directly proportional to its frequency f and is given by E = h f where h is called Planck’s constant and has a value given by h = 6.626 × 10 -34 J.s = 4.136 × 10 -15 eV.s 1eV = 1.602 × 10 -19 J

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Reflection of Light The ray of light that strikes the surface is called the incident ray . The ray that leaves the surface is called the reflected ray. A perpendicular line drawn to e surface at the point of the surface at the point of incidence is called the normal . The angle between the incident ray and the normal is called the angle of incidence The angle between the reflected ray and the normal is called the angle of reflection. Reflected light obeys the law of reflection, that the angle of reflection equals the angle of incidence.
Images on a plane mirror The image produced by a plane mirror is due to reflection of light. The diagram below shows how the light originating from an object get reflected after falling on a plane mirror, and the reflected rays gives us the illusion of an image behind the mirror.

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An image produced by plane mirrors have the following properties. 1. The image produced is upright 2. The image is the same size as the object (i.e., the magnification is m = 1) 3. The image distance d i = the object distance d o 4. The image is a virtual image, because it is not by the actual meeting of the reflected rays, and it cannot be caught in a screen.
Curved Mirrors Laws of reflection are also obeyed on curved mirrors. Depending on the curvature of the reflecting surface, there are two types of curved mirrors. A mirror with its reflecting surface curved inward is called a concave mirror and the one with its reflecting surface curved outward is called convex mirror

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Center of curvature (C) : A curved mirror is part of a sphere nd the center of that sphere is called the center of and the center of that sphere is called the center of curvature of the mirror. Principal axis : A line passing through the center of curvature and containing the center point (also called the pole of the mirror) of the mirror is called the principal axis. Radius of curvature (R): The distance from the pole of the mirror to the center of curvature is called the radius of curvature.
Principal Focus (F): In the case of a concave mirror, a ray that is parallel to the principal axis incident on the mirror, after reflection, will pass through a fixed point on the principal axis. This point is called the principal focus of the concave mirror. While the principal focus of a concave mirror is a real point, the principal focus of a convex mirror is a virtual point. Focal length ( f ):

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Lesson_4.6_Printable_PPT - Properties of Light The present...

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