Class1

# Class1 - Nature of Light Light is both a wave and a particle in a non-classical sense Wave property(1 light can have interference and diffraction(2

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Nature of Light Light is both a wave and a particle in a non-classical sense. Particle property (1) light shows particle nature when interacting with matter, such as absorption and emission (2) its energy is quantized, in quanta of E = hv, called photons (3) the photon is a massless (the rest mass = 0, recall relativistic mass definition) and chargeless particle (4) photon moves at the speed of light with momentum: p = h/ λ Wave property (1) light can have interference and diffraction (2) it is a part of electromagnetic spectrum, λ from 400 to 800 nm (this is the visible spectrum for a human eye –> our definition of light . But all e.m. waves obey same physics, no matter λ .) (3) it is described by Maxwell wave equations, requires no medium to propagate Planck’s constant: h = 6.626x10 -34 J.s Speed of light in vacuum: c = 2.998x10 8 m/s

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http://en.wikipedia.org/wiki/ Electromagnetic_spectrum
Geometrical Optics Wave nature of light does not play a significant role, no diffraction is considered. limit {Wave Optics} ----------> {Geometrical Optics} λ Æ 0 Both dimension of the optical system and image formed by the system >> λ In geometrical optics, rays are used to trace the light propagation Ray: line drawn in space corresponding to the direction of light propagation 1. Rectilinear propagation of light In an uniform media, light propagates in a straight line. Its speed in the medium is given: n : index of refraction c : speed of light in vacuum e.g. in air and vacuum, n = 1; for most glass, n 1.5 n c v =

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Laws of Reflection and Refraction When a ray of light is incident on the boundary separating two different media, part of the ray is reflected back into the first medium and the reminder is
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## This note was uploaded on 10/19/2009 for the course PHY 31 taught by Professor Cebe during the Fall '08 term at Tufts.

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Class1 - Nature of Light Light is both a wave and a particle in a non-classical sense Wave property(1 light can have interference and diffraction(2

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