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- Thread starter asifmumtaz
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band gap in solids arises due to lattice potential.this lattice potential has max. effect at zone boundary.band gap is produced at zone boundary due to bragg reflection of travelling wave.after reflection it becomes standing wave instead of travelling wave?howz this possible?plz help

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Yes, bandgap arises from the bragg reflections at the zone boundary. the traveling wave becomes a standing wave - I agree. How is this possible? The mathematical definition of traveling wave is: Amplitude * cos( k * x - omega * t), where k is the wavevector of the wave, omega is its characteristic frequency, x and t are spatial and time coordinates. When traveling wave suffers a reflection off the zone boundary there's an equal but opposite traveling wave (reflected part). By superposition then, the total k of the wave is zero - hence standing wave.

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