Sunday, 6 November 2016

nature of light


Light:  The physical cause, with the help of which our eyes experience the sensation of vision, is known as light.  (or) the form of energy, which excites our retina and produce the sensation of vision, is known as light.

Ray of light:   The path of light energy from one point to another is known as a ray of light.

properties of light:  i) No material medium is required for the propagation  of light energy i.e. it travels even in vacuum.

ii) Its velocity is constant in all inertial frames.  It is independent of the relative velocity between source and the observer.

iii) velocity of light is maximum in vacuum whose value is 3 x  m/s.

iv) Light can emit electrons from the metal surface i.e. it can produce photoelectric effect.

v) Light propagates in straight lines.

vi) Light produce thermal effect and exerts pressure when incident upon a surface.  It proves that the light has momentum and energy.

vii) Light exhibits the phenomena of reflection, refraction, interference, diffraction, polarisation, and double refraction.

viii) The properties of the medium through which light passes remain unchanged.

ix) The velocity of light is different in different media.  In rarer medium, it is more and in denser medium, the velocity of light is less.


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