Physics: Intro to Nuclear Physics Notes

The four forces in the universe: gravity, strong force, weak force, electromagnetism
Gravity is attraction between objects
Gravity is only significant for very large objects

Electromagnetism Creates magnetism

The Strong Force

The glue that binds the nucleus together
When you release the energy in the nucleus, you get a nuclear bomb and nuclear energy

Fission

Very large unstable nuclei can fall apart or can be split
Purpose is to create large amounts of energy

Nuclear Chain Reaction

Fusion

Occurs under high pressure and temperature
Small nuclei combine to form large nuclei
Cannot be controlled
The Sun turns hydrogen into helium
Heavier elements are made in supernovas and in star collisions
Huge amounts of energy are released by fusion
Used in hydrogen bomb (not WW 2 Bomb) and stars
Albert Einstein determined that a small amount of mass contains a large amount of energy
Equation: E+mc^2

The amount of mass lost when the WW2 Bombs dropped on Japan: 0.7 grams
The amount of mass the Sun converts to energy each second: 5 million tons
The amount of years till the Sun runs out of fuel (hydrogen): 5 billion years

The Weak Force

Beta decay is responsible for

Carbon Dating

Wave Particle Duality

Light can behave like a wave or a particle
Light is a transverse wave
Light does not need a medium
Light also travels in particles called photons
Young’s Double Slit Experiment showed that light can behave as both a particle and a wave
Two waves combine form an interference wave

Spectroscopy

Elements can be identified by their atomic spectrum
Each type of light corresponds to a specific energy
Visible light spectrum in order from least to greatest energy “ROY-G-BIV” Highest energy is violet, lowest energy is red
Higher orbits have higher energy

Photons are emitted from the atom when an electron falls in energy
The color of the photon emitted is related to the amount of energy released
Spectroscopy: dispersion of light into its available spectrum

the two types of spectra: continuous, discrete
In a continuous spectrum, light is composed of a wide unbroken range of colors
Materials that create a continuous spectrum: stars and galaxies
A discrete spectrum only has lines at very distinct colors
Every element and chemical has a different emission spectrum

The Photoelectric Effect

Einstein won the Nobel Prize in 1921for the photoelectric effect
The photoelectric effect: the emission of electrons when electromagnetic radiation (light) falls on an object

The threshold frequency is the minimum energy required to eject an electron
If energy is below the threshold frequency, no emission
If energy is equal to or greater than the threshold frequency, electron emitted
Only the frequency determines the energy
The amount of light (intensity) does not matter
Different substances have different thresholds
Different light has different energy