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PHYSICS Quantum Phenomena:

1. Photoelectricity:

A photon is a packet of energy.

Metal contains conduction electrons, which move
freely inside the metal. The electrons collide with each
other and with positive ions of the metal.

If you shine a light of high enough frequency onto the
surface of a metal,…

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Photoelectrons are emitted with a variety of kinetic energies ranging from zero to a
maximum value. This value of maximum kinetic energy increases with the frequency of
the radiation, and is uneffected by the intensity of the radiation.
There is no time delay between absorbtion and emission.


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circuit can be used to measure the photelectric current. This is proportional to the number of
electrons per second that transfer from the cathode to the anode.
· Photoelectric current = I/e (where is e is the charge of the electron)
· photoelectric current is proportional to the intensity of…

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· adding electrons=negatively charged ion
· removing electrons=positively charged ion
· process of creating ions is known as
· A photon can be absorbed and cause
ionisation if its energy is greater than or equal to
the difference between the ionisation level and
ground state.

For example:

1)alpha, beta…

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4. Energy levels in atoms:

Electrons in atoms:
· electrons in atoms are trapped by the electrostatic force of attraction of the
· The move in shells surroundind the nucleus
· electron in an inner shell has less energy than an electron in an outer shell.
· Each shell…

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· Process by which electrons can 'relax' from
their excited state.
· When an atom deexcites it moves from a
high energy level to a lower energy level. In doing so
it releases a photon with the energy equal to the
energy lost by the atom.
· Energy of…

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An atom in an excited state can deexcite directly or indirectly to
the ground state. Therefore an atom can absorb photons or certain
energies and then emit photons of the same or lesser energies. As
shown below.

The above process explains why substances fluoresce/glow with visible light when they absorb…

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· Since only certain photon energies are allowed, you only see the corresponding
· No other element produces the same pattern of light wavelengths.
· This is because the energy levels of each type of atom is unique. Therefore the photons
emitted are characteristic of the atom.

6. Wave…

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Dual nature of electrons (MATTER WAVES):
· particlelike nature: electrons in a beam can be deflected by a magnetic field.
· wavelike nature: de broglie's hypothesis, that electrons can be diffracted.

De broglie's hypothesis and wavelength:
· de broglie's wavelength is related to the momentum, p, of the particle


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