Page 1 - Lesson note reflection of light
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SAI INTERNATIONAL SCHOOL
                                                      PHYSICS
                                                      CLASS X
                             Chapter: LIGHT(REFLECTION & REFRACTION)




               LESSON NOTES:

               Introduction to Light


                             Light is a form of energy due to which we are able to see the objects
                       which emits light for example objects like sun, lamp, candle emits light of their
                       own and thus they are known as luminous objects.
                             There are objects like table , chair etc. which are not luminous objects
                       and still we are able to see them and this happens because they reflects lights
                       which falls on them from a luminous object like sun, lamp etc. and when this
                       reflected light reaches our eyes we are able to see such non luminous
                       objects.
                             Light rays basically consist of electromagnetic waves which do not
                       require any material medium (like solid, liquid or gas) for their propagation.

               Wavelength of visible light waves is very small and is of the order
               of 4×10−7m to 8×10−7 m.


               Speed of light waves depends on the medium through which they pass as speed of
               light in air is slightly less than the speed of light in vacuum 8×108m/s8×108m/s same
               way speed of light in water and glass is much less than that in air.


                     When light falls on the surface of an object it can either be
                          1.  Absorbed:- If an object absorbs all the light falling on it , then it will
                              appear perfectly black for example a blackboard
                          2.  Transmitted: - An object is said to transmit light if it allows light to pass
                              through itself and such objects are transparent.
                          3.  Reflected:- If an object sends back light rays falling on its surface then
                              it is said to have reflected the light

               Reflection of Light


                     The process of sending back light rays which falls on the surface of an object
                       is called REFLECTION of light
                     Silver metal is one of the best reflectors of light.
                     Mirrors we use on our dressing tables in our home are plane mirrors.
                     A ray of light is the straight line along which the light traveled and a bundle of
                       light rays is called a beam of light.
                     Laws of Reflection of light
                          1.  The angle of incidence is equal to the angle of reflection, and
                          2.  The incident ray, the reflected ray and the normal to the mirror at the
                              point of incidence all lie in the same plane.


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