Modern Physics Flashcards
What are the two simple postulates that Einstein made about special relativity?
1 . All the laws of physics are the same in every uniformly moving frame of reference.
2. The speed of light in a vacuum is always measured to be c = 3 x 10^8 m/s no matter the motion of the source of the light or the motion of the receiver of the light.
What does the second postulate mean in regards to time and space?
Time and space cannot be constant. The faster you go, the slower time moves and the shorter distances become in the direction you are going. Due to postulate one, you will not notice any of these changes.
What is an electron-volt?
The amount of energy required to change the potential of an electron by one volt.
What happens if a photon loses momentum and energy?
The wavelength increases and the frequency decreases.
In regards to wave-particle duality, what are the characteristics of long wavelengths such as radio waves.
They deomonstrate lots of wave behaviors due to their long wavelength.
They dont exhibit much in the way of particle properties due to their low energy.
In regards to wave-particle duality, what are the characteristics of short wavelengths such as gamma waves.
They exhibit lots of particle properties due to their high energy.
They demonstrate little in wave behaviours due to their short wave length.
What’s an alpha particle?
Two protons and two neutrons stuck together. (heavy)
What’s a beta particle?
An electron or a positron.
What’s a positron?
The antimatter equivalent of an electron. Same mass and charge as an electron, but a positive sign on its charge.
What’s a gamma particle
A gamma ray photon. (massless and chargeless)
What is α decay?
Happens when a nucleus emmits an alpha particle.
What is β decay?
Happens when a nucleus emmits a positron or an electron.
What occurs during a β+ decay?
A proton turns into a neutron and emits a positron.
What occurs during a β- decay?
A neutron turns into a proton. The change in charge is acounted for by the emitted electron.
What occurs during ɣ decay?
A gamma particle is a photon, with no mass or charge. A nucleus undergoing gamma decay does not change its outward appearance.
What is neutron decay?
A neutron is emmited from the nucleus. Because a neutron has a mass of one, and no charge, only the mass number of the nucleus changes. This results in a different isotope.
What is the mass defect?
The differnence in mass that is convertedinto kinetic energy during nuclear reactions.
What is conserved during nuclear reactions?
- Mass/Energy
- Momentum
- Charge
- Nucleons (the sum of neutrons and protons)
What is half-life?
The time it takes for half of he radioactive atoms to decay?
Decay rates appear to be independent of what external conditions?
Decay rates are independent of all external conditions.
What is fission?
Fission occurs when a heavy nucleus is split into two relatively large chunks. This begins by shooting a neutron into the nucleus, which initiates the reaction. Large amounts of energy are created as mass converts to energy.
What is fusion?
Ocurs when two light nuclei combine to make a new heavier and more stable nucleus. Large amounts of energy are released in the reaction.
What is an induced reaction?
When a nucleus is bombarded with high-speed particles.
What is antimatter and annihilation?
When matter and antimatter meet, they annihilate each other. This converts all of their mass into energy.
What is nuclear binding energy?
A small amount of the mass of the nucleus is converted into energy, which holds the nucleus together.
What is radiation?
The emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles that cause ionization.
What is 1 u equivilent to?
1.66 x 10^-27 kg or 931 MeV/c^2
