Unit 5: Nuclear Physics Flashcards
(27 cards)
What is relativity?
Relativity is the study of how different observers measure the same event. Relativity can be divided into general relativity and special relativity
Special relativity
Deals with observers who are moving at a constant velocity
General relativity
Deals with observers who are undergoing acceleration
Length contraction
The length of an object moving at relativistic speeds (speeds close to the speed of light) undergo a contraction along the direction of motion. It is only significant when an object is moving at relative speeds and contraction only occurs in direction in which object is moving
Time dilation
Time passing slower for an observer who is moving relative to another observer. (Moving clocks run slowly due to high speeds). Twin theory explains if a twin travels near the speed of light and returns to earth, the twin on earth will age normally (clock runs normal) twin who left earth will return only aged half of what other twin did.
Relativistic Mass
The more mass something has, the more energy is required to move it. To move something of an infinite mass would require infinite energy which is not possible, so nothing can travel faster than the speed of light.
Time travel theory
Relativity shows travelling to the future is easy if you can reach the speed of light. In the twin theory, the twin who leaves earth returns to the future since the clocks run at half the speed in space. Travelling back in time is impossible. This would require travelling faster than the speed of light. According to the theory, we should be able to time travel, but cant because we can’t travel at the speed of light.
Quantum mechanics
A branch of science studying the very small. Its an attempt at understanding the microscopic world around us and how it differs from the macroscopic world.
***What is a blackbody?
A blackbody is a THEORY considered an ideal radiatir that absorbs all light and reflects none, it is jet black. The sun is considered a perfect blackbody. It absorbs almost all wavelengths of electromagnetic radiation WITHOUT REFLECTION. The light we see emitted from the sun is a result of ITS TEMPERATURE. It emits radiation at the yellow part if the spectrum
Photon
The fundamental particles of light. They have no mass and no charge. They are both a particle and a wave
Photoelectric effect
When light strikes a material and ejects electrons from then producing electric currents. Hits surface as wave, ejects particles. As intensity of light increases, more electrons are ejected but without an increase in energy. This effect is the basis behind quantum nature of life
Double slit experiment
High frequency photons produce waves
Low frequency photons produce particles.
Theories of quantum mechanics
Schrodingers cat
- Multiverse
2: Copenhagen theory
3: Collapse theory
4: Pilot wave theory
5: Simulation theory
(Look in book for explanations)
The nucleus
Made up if protons and neutrons. Protons are positively charged, electrons are negatively charged, creating attractive force. A strong force, 100x stronger than the electromagnetic force, holds the protons to protons, neutrons to neutrons, and protons to neutrons. The difference between the sum if the parts of a nucleus and the actual nucleus is the mass defect.
Binding energy
To pull a nucleus apart you must do work to overcome strong nuclear force. Do work adds energy to the system called binding energy. All binding energies are negative because the assembled nucleus has less energy
Radioactivity
The spontaneous changing of the nuclei atoms from one element to another. As the element changes, particles and radiation is given off.
*Alpha Particles
-Helium particles with 2 protons and neutrons
-Positively charged
-Ejected at high speeds (but slowest of all three rays)
-Travel only a few cm in air
-Low penetrating power.
Beta Particles
-Stream of electrons
-Negatively charged
-High speeds approaching speed of light.
-Lower mass than alpha-> greater speed.
-Higher penetrating power
-POSITRON IS BETA PLUS PARTICLE
Gamma Rays
-Waves NOT particles.
-Have no mass or charge
-Travel at speed of light
-High energy electromagnetic radiation with short wavelengths (photons)
-Highest penetrating power
Sources Of Radioactivity
-Radon gas from ground, buildings, food and drink, cosmic radiation, artificial sources like nuclear power and weapons test, medical, and other sources.
Biological effects of radiation
-Mutations
-As dose of radiation increases, body shuts down.
-reduction in blood cell count, nausea, vomiting.
-Malfunctioning of small intestines and blood systems
-more than 20sv fatal within hours due to collapse of central nervous system
Radiation controversy
Experts agree that radiation can and does cause observable health effects at high doses.
Low doses however might not damage the cells or might damage the cell but can be repaired. The study for human exposure to small doses is not consistent. Some show no change in rate of disease , some show decrease in disease, some show increase.
Radioactive decay
The changing of one element into another is transmutation.
When nucleus if a radioactive atom changes inti a different type of atom by emitting a radioactive particle. Also know as radioactive decay.
Alpha decay
Mass decreases by 4 atomic # decreases by 2
