Physics: Cathode Ray Tube Experiments

Atomic Physics

• Images of various materials are used to illustrate the concepts, including a variety of patterns of colored circles, a notepad, and an image of an atom.
• The program of studies checklist details topics for understanding the electrical nature of the atom.
• Knowledge outcomes cover describing matter containing discrete charges, explaining cathode ray contributions, J.J. Thomson's experiment, Rutherford's scattering experiment, and the significance these experiments had for the understandings regarding the size and mass of the nucleus and atoms.
• Performing and recording outcomes require students to perform experiments or use simulations to find the charge to mass ratio of the electron.
• Analyzing and interpreting outcomes expect students to find the mass of an electron or ion, and derive formulas for the charge-to-mass ratio.
• Communication and teamwork outcomes include selecting and using numeric, symbolic, graphical, and/or linguistic modes of representation.

Quantization of Energy in Atoms and Nuclei

• Knowledge outcomes include explaining the emission of electromagnetic radiation (EMR) by accelerating charged particles, explaining continuous and line-emission/absorption characteristics, and explaining stationary states to explain observed spectra of atoms and molecules.
• Students are expected to calculate energy difference between states, using conservation of energy and observed characteristics of emitted photons.
• Initiating and planning outcomes require predicting conditions necessary for line-emission, and line-absorption spectra.
• Predicting possible energy transitions in the hydrogen atom, using a labeled diagram of energy levels is also part of the outcomes.

Nuclear Fission and Fusion

• Students are expected to describe the properties of alpha, beta, and gamma radiation, write nuclear equations, perform half-life calculations, compare and contrast fission and fusion reactions, and relate mass defects to energy released in reactions using Einstein's mass-energy equivalence.
• Outcomes include predicting the characteristics of decay products and analyzing interpreting data from radioactive decay and estimating half-lives of radioactive decay chains.

Structure of Matter

• Students are expected to explain how particle tracks contributed to the discovery and identification of subatomic particle characteristics, explain qualitatively the strong nuclear force's role in high-energy particle accelerator use, and describe the composition of protons and neutrons from quarks.
• Outcomes include comparing and contrasting the properties of up quarks, down quarks, electron neutrinos, and their antimatter counterparts in regard to charge and energy(mass-energy), describing beta-positive and beta-negative decay using first generation elementary fermions, and principles of charge conservation.

Atomic Physics Vocabulary

• This section provides a table with blank spaces for students to complete with their own researched terms and definitions.

Discovery of the Electron

• John Dalton's theory of elements and structures described that elements are made up of smaller atoms.
• J. J. Thomson's experiments on cathode rays led to the discovery of the electron.
• 3rd experiment details were: measuring properties to determine charge to mass ratio of electrons, combining work of others.
• Thomson's experiments used cathode ray tubes to test if negative charges could be separated from moving cathode rays using a magnetic field.
• A series of experiments eventually led to a calculation that was able to determine the charge to mass ratio of electrons.

Discovery of the Nucleus

• Rutherford's experimental setup used radioactive materials to emit alpha particles, a thin gold sheet, and a zinc-coated screen.
• Based on the expectations from Thomson's model, the effect on positive charges could produce small scattering angles, that is why negatives were considered irrelevant and not causing many significant scattering angles.
• Unexpectedly, some alpha particles were scattered at very large angles or bounced straight back, contradicting Thomson's model.
• This led Rutherford to propose a new model of the atom with a tiny, dense, positively charged nucleus at the center, surrounded by electrons.

Thomson's Model

• Thomson's model was a plum pudding model of an atom to illustrate the concept of positive and negative particles in the atom's structure.

Rutherford's Model

• Rutherford's model consisted of a very small and dense positive nucleus at the center of the atom. Negatively charges electrons are surrounding the nucleus.
• Empty space surrounds the nucleus.

Bohr Model of the Atom

• Rutherford's model had serious flaws that needed to be addressed; electrons were orbiting in a circular pattern (that is accelerating).
• Maxwell's ideas stated that accelerating charges must emit energy. This meant that electrons should be losing energy and spiraling into the nucleus.
• Bohr's model proposed discrete energy levels for electrons.
• Electrons can only be in specific energy levels, and transitions between these levels produce the colors in the spectrum.

Continuous and Emission/Absorption Spectra

• Passing white light through a spectroscope produces a continuous spectrum.
• Each element has a unique emission and absorption spectrum, similar to a 'fingerprint'.
• Observation of a black/dark lines (absorption) on the colored background (emission), showing that the wavelengths of light emitted or absorbed by different elements are unique.

Energy Levels and Hydrogen

• Bohr calculated the energy and radius of the lowest energy levels for hydrogen.
• Transitions between energy levels result in emitted or absorbed photons, with specific wavelengths.

The Quantum Model

• Bohr's model had problems with electrons emitting radiation when in stable energy levels, and the actual lines are a combination of two or more closely spaced lines.
• De Broglie showed that particles have wave-like properties.
• For the wavelength of the electron to fit perfectly around the nucleus, the circumference of the electron orbit must be a whole number of wavelengths.

The Nucleus

• The nucleus contains nucleons.
• Protons have a positive charge, determine the element, and their number equals atomic number.
• Neutrons have no charge. The total of protons and neutrons is the atomic mass number.
• The notation for a particular nucleus utilizes the atomic number (Z), atomic mass number (A), and the element's symbol.
• Isotopes have the same atomic number but different numbers of neutrons, potentially affecting nuclear stability.
• The strong nuclear force overcomes the electrostatic force of repulsion between protons to hold the nucleus together.
• Calculations measure the mass defect and binding energy of a particular nucleus.

Radioactive Decay

• Radioactive decay occurs in unstable atoms and releases energy.
• Alpha decay emits a helium nucleus.
• Beta decay involves a neutron converting to a proton and emitting an electron.
• Gamma decay involves emitting high-energy photons from an excited nucleus.
• Half-life is the time it takes for half of the atoms in a sample to decay.

Decay Rates

• The concept of half-life is detailed.
• Calculating quantity remaining after an amount of time using the equation for exponential decay.

Fusion and Fission

• Fusion is the combining of light nuclei, while fission is the splitting of heavy nuclei.
• Fusion in stars involves the proton-proton chain.
• Fission reactions can be used in power plants; this involves a chain reaction that is carefully controlled.
• Fission reactions are used in nuclear weapons that are explosive chain reactions.

Detecting and Measuring Subatomic Particles

• Methods of detecting/measuring particles include scattering events, decays, and examining bound states.
• Methods such as Cloud Chamber and Bubble Chambers.
• The use of magnetic fields to curve the paths of charged particles allows for the identification of their nature and mass.
• Photographs showing particle tracks are analyzed based on characteristics, such as particle charge and mass determination.

Energy Requirements

• The energy required to study subatomic particles.
• Particle accelerators are discussed and related to the energy needs for subatomic particles' studies.

Particle Accelerators

• Different types of particle accelerators (Van de Graaff, Drift tube, Cyclotron, and Synchrotron) are included.

Units for Subatomic Masses

• Energy units (eV, MeV) are convenient to use for subatomic particles' calculations.
• Conversion between mass and energy units is presented.

The Standard Model

• All matter is made of 12 fundamental particles (6 leptons and 6 quarks).
• The Standard model includes the electromagnetic, weak, and strong nuclear forces.
• Quarks are grouped together through the strong force.

Test your knowledge on the fundamentals of cathode ray tube experiments, focusing on electric and magnetic fields, electron paths, and mass defect calculations. This quiz explores key concepts such as charge to mass ratio and particle interactions in physics.