Unit 7: Quantum, Atomic, and Nuclear Physics

Quanta

Quanta

Light being emitted as individual packets of constant energy called quanta.

Photon

A quantum of electromagnetic energy is known as a photon.

Photoelectric effect

Light behaves like a stream of photons, and this is illustrated by the photoelectric effect.

Photoelectrons

The released electrons are known as photoelectrons.

Wave theory of light predictions:

• The significant time delay between the moment of illumination and the ejection of photoelectrons.

• Increasing the intensity of the light could cause the electrons to leave the metal surface with greater kinetic energy.

• Photoelectrons would be emitted regardless of the frequency of the incident energy, as long as the intensity was high enough.

Atomic Spectra

The light from a glowing gas, passed through a prism to disperse the beam into its component wavelengths, produces patterns of sharp lines called atomic spectra.

The wavelength of photon

Photon’s wavelength:

• λ = wavelength

• c = speed of light

• f = frequency

• h = Planck’s constant (6.626 × 10 -34 joule·s)

De-Broglie Wavelength

De-Broglie wavelength explains matter's wave-like behavior in quantum mechanics.

The equation is λ = h/p, where λ is De-Broglie wavelength, h is Planck's constant, and p is particle momentum. As momentum increases, the wavelength decreases.

This is important for understanding particle behavior at the quantum level.

Wave-Particle Duality

Electromagnetic radiation propagates like a wave but exchanges energy like a particle. This is known as wave-particle duality.

The wave function

The probability that a particle will be measured to be at a particular position when the position is measured. That probability is related to a new physical parameter called the wave function.

Theory of relativity

The results of physical experiments will be the same in any-nonaccelerating reference frames.The speed of light is constant.

Time dilation

Demonstrated by synchronized atomic clocks.

Length Contraction

To be consistent with time dilation, there must also be disagreement about distances. This is known as length contraction.

Isotopes

The nuclei that contain the same number of neutrons are called isotopes.

Mass number

The total number of nucleons (Z+N), is called the mass number, and is denoted by A

Atomic number

The number of protons in a given nucleus is called the atom’s atomic number denoted by Z.

Nuclear force

The strong nuclear force is a fundamental force which binds neutrons and protons together to form nuclei.

Binding energy

It tells us how strongly the nucleus is bound.

Nuclear fusion

It is of small nuclei at extremely high temperatures.

Nuclear fission

The emission of a particle or splitting of the nucleus.

Decays

Alpha, Beta, and Gamma decay:

Disintegration energy

It involves emission or absorption of energy