Monday, February 4, 2008

Wave-particle duality

The earliest view of light, due to Newton, regarded light as made up of particles (commonly termed as corpuscles of light). The particle nature of light explained some of the experimental facts such as reflection and refraction of light. However, using particle nature of light, phenomena of interference and diffraction could not be explained. (See relevant chapters in Physics text and link that material with this idea).

Huygens proposed wave like character of light. With the help of wave theory of light, Huygens explained the phenomena of interference and diffraction as well as reflection and refraction. Hence the corpuscular theory was discarded and wave theory was adopted.

But once again, phenomena such black body radiation and photoelectric effect needed explanation. Wave theory could not explain these phenomena.

Einstein has suggested that light can behave as a wave as well as a particle i.e., it has dual character.

Characteristics of electromagnetic radiations

(i) The consists of electric and magnetic fields that oscillate in the directions perpendicular to each other and perpendicular to the direction in which the wave is traveling

(ii) These electromagnetic radiations do not require any medium for propagation.

(iii) All waves are characterized in terms of their wavelengths, frequency, velocity and amplitude.

Velocity of a wave = wavelength * frequency

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