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CHAPTER - 11
DUAL NATURE OF RADIATION AND MATTER
SYNOPSIS :
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A photon has zero rest mass but a photon of energy E possesses a mass equal to E/c2 and
momentum equal to E/c.
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A particle can behave both as a particle and wave but in a given situation, it behaves either
as a particle or as a wave.
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“Some say that the only thing quantum theory has going for it is unquestionably correct.”
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De-Broglie waves are matter waves i.e. waves altogether different from electromagnetic
waves.
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Don’t try to work out the momentum of a high speed particle and hence its de-Broglie
wavelength using its rest mass. Mas increase significantly as the speed of the particle
approaches the speed of light!
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When a particle exhibits wave nature, it is associated with a have packet, rather than a
wave.
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As the accelerating voltage is increased, de-Broglie wavelength of electron decreases.
{Std 12th Physics CBSE - Ch 11. Dual nature of radiation and matter - Synopsis}
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Since phenomenon of diffraction is exhibited by waves, electrons must be behaving as
waves in Davisson and Germer experiment.
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“If one does not feel dizzy when discussing the implications of Planck’s constant, it means
that one does not know what one is talking about.”
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The stopping potential (in volt) is numerically equal to the maximum kinetic energy of
photo electrons in eV.
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Photoelectric effect demonstrates particle nature of radiation.
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If light were waves (not photons), it will take about a year to eject a photoelectron out of
the metal surface!
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There is no effect of intensity of incident light on the kinetic energy of the emitted
photoelectrons.
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There is no effect of frequency of incident light on the number of the emitted
photoelectrons.
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A photon is not a material particle. It is a quanta of energy.
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Brighter light means more photons, not more energetic photons!
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Low intensity of the incident light does not mean delay in photoelectric emission!
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Photoelectric effect is a one photon – one electron phenomenon. One photon cannot eject
more than one photoelectron.
{Std 12th Physics CBSE - Ch 11. Dual nature of radiation and matter - Synopsis}
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A photocell converts a change in the intensity of incident light into a change in
photocurrent.
{Std 12th Physics CBSE - Ch 11. Dual nature of radiation and matter - Synopsis}