Physics: Energy and Momentum Concepts

Kinetic Energy

• Kinetic energy is the amount of work an object can perform when its speed is reduced to zero.
• Formula: KE = 1/2 * m * v²
• Unit: Joule

Electron Volt (eV)

• Electron volt is a unit of energy.
• Equivalent to the kinetic energy gained by an electron accelerated through a 1V potential difference.

Force

• Force is a vector quantity.
• Characterizes the ability to cause acceleration.

Momentum

• Momentum is a vector quantity.
• Product of mass and velocity: p = m * v

Electromagnetic Spectrum

• Electromagnetic spectrum components, in ascending energy order:
  • Radiowaves
  • Microwaves
  • Infrared
  • Visible light
  • Ultraviolet
  • X-rays
  • Gamma rays

Visible Light

• Range of electromagnetic radiation detectable by the human eye (approximately 400-750 nm).

Limiting Frequency (fmax)

• Maximum frequency of braking radiation.
• Formula: fmax = eU/h, where U is voltage, e is charge of electron and h is Planck's constant.

X-ray Absorption Mechanisms

• Three primary mechanisms:
  • Photoelectric effect
  • Compton effect
  • Pair production

Photoelectric vs Compton Effect

• Photoelectric effect: X-ray energy is used to ionize the atom and give kinetic energy to the electron.
• Compton effect: Only part of the photon's energy is used for electron emission, the rest is scattered.

Laser Light Characteristics

• Monochromatic
• Coherent (in time and space)
• Low divergence
• High intensity

Laser-Tissue Interactions

• Photothermal (thermy, coagulation, vaporization, carbonization)
• Fluorescence/photochemical reactions
• Photodissociation
• Multiphoton ionization

Light Intensity and Absorbance

• 10-fold decrease in intensity for each unit increase in absorbance.

Molar Extinction Coefficient

• Absorbance of a 1M solution with a 1cm path length.

Protein/Nucleic Acid Absorption

• Characteristic absorption maxima:
  • Proteins (280 nm)
  • Nucleic acids (260 nm)

Amino Acids with High Absorption

• Tyrosine (Tyr)
• Tryptophan (Trp)
• Phenylalanine (Phe)

Singlet and Triplet States

• Singlet state: zero unpaired electrons. Spin multiplicity = 1.
• Triplet state: two unpaired electrons. Spin multiplicity = 3.

Excited Electronic State Relaxation in Molecules

• Vibrational relaxation
• Internal conversion
• Intersystem crossing
• Fluorescence
• Phosphorescence
• Delayed fluorescence
• Energy transfer

Fluorescence Lifetime

• Time required for the number of excited molecules to decrease to 1/e (approximately 37%) of initial value.

Scintillation, Chemiluminescence, Photoluminescence

• Scintillation: photon emission due to ionizing radiation.
• Chemiluminescence: photon emission due to a chemical reaction.
• Photoluminescence: photon emission due to excitation by photons.

Fluorescent Measurements

• DNA, RNA, protein, and lipid content of a cell
• Membrane permeability
• Intracellular enzymes
• Membrane potential
• Intracellular calcium level
• Intracellular pH

Shortest Resolvable Distance (Light Microscope)

• Approximately 200 nm

Isotopes

• Variants of an element with same atomic number but different mass numbers.

Nucleon Energy Levels

• Nucleons in nuclei reside at lower energy levels compared to free particles.

Radioactive Decay: Atomic Number and Mass Number Changes

• Decay types and associated changes in atomic and mass numbers tabulated.

Radioactive Decay Equation

• Equation describing the number of undecayed radioactive nuclei over time (N=Noe^(-λt)).

Effective, Physical, Biological Half-lives

• Interrelation formula provided.

Ionizing Radiations

• Alpha and beta- radiations are directly ionizing due to their charge.

GM-Counter Detection

• Detects alpha, beta, and gamma particles

Scintillation Detector Detection

• Converts radioactive particle energy to luminous energy (light flashes).

Radioactive Radiation Penetrability

• Alpha < Beta < Gamma

Biological Effects of Irradiation

• D37 (dose required for 37% survival)
• Radiations damage in aqueous solutions

Effective Dose

• Weighted sum of equivalent doses in different tissues/organs
• Used because radiation sensitivity differs among tissues

Factors Determining Radiation Sensitivity

• Radiation quality
• Time factor
• Temperature
• Oxygen effect
• Protective substances

Cell Survival Model (Linear-Quadratic)

• Equation modeling cell survival with dose.

Cell Cycle Radiosensitivity

• Cells most sensitive during mitosis and most resistant during late S phase.

SPECT

• Images taken from different directions using a gamma camera.
• Used to determine distribution of radioactive source.

SPECT Isotopes

• Nuclei used in the SPECT process.

Computer Tomography

• X-ray images from multiple directions to determine 3D structure.

NMR Active Nuclei

• Nuclei with non-zero nuclear spin.

Biological Applications of NMR

• Nuclei used for biological applications.

Macroscopic Magnetic Field Consequence

• When nuclei's magnetic moments are aligned with an external field, macroscopic magnetization occurs (either equilibrium/longitudinal).

MRI Image Parameters

• Reveals 1H nuclei density and relaxation rates.

In Vivo MRS

• Non-invasive technique to show metabolic processes in living tissue using NMR spectroscopy.

Ultrasonic Frequency Range

• Audibly detectable sound frequencies for humans.

Sound Intensity Definition

• Rate of sound energy traveling through unit area.

Medium Compressibility

• Change in volume relative to pressure increase.

Ultrasound Generation Method

• Methods applicable for ultrasound generation.

Frictional Force (in aqueous environment)

• Force acting on a molecule due to friction in an environment.
• Formula: Fr=-fv

Diffusion Constant

• Physical quantity representing diffusion.
• Units (m²/s).

Fick's First Law

• Law describing concentration-driven material transfer.
• Constants and interpretation provided.

Diffusion Equilibrium Factors

• Parameters that tend to equilibrium in diffusion.
• Example: Chemical potentials.

Osmotic Pressure

• Pressure that prevents solvent flow into a solution.

Lipid Membrane Motion Forms

• Lipid movement in cellular membranes.
• Examples: Lateral diffusion, rotational diffusion, membrane flip-flop.

Membrane Properties Changes

• Factors impacting membrane transition temperature.
• Example: Fatty acid saturation, chain length.

Membrane Permeability

• Permeability for apolar and other molecules

Extra/Intracellular Ion Concentrations

• Concentrations for key ions listed.

Facilitated Diffusion

• Passive transport aided by transport proteins.

Ion Channel Activation

• Categorization based on activation mechanisms.

Ionophores

• Grouping based on ion transport mechanisms

Resting Membrane Potential Maintenance

• Factors contributing to maintenance of membrane's resting potential.

Equilibrium Potential

• Membrane potential where net flux of a given ion is zero (thermodynamic equilibrium).

Goldman-Hodgkin-Katz Equation

• Equation relating resting membrane potential to ion permeabilities and concentrations.

Eye Resolution

• Smallest visual angle for distinguishing two points.

Photoreceptor Triggering

• Photons trigger receptor chemical processes.

Phon Scale vs Bel Scale

• Phon scale uses normalized intensity of 1000Hz sound to evaluate loudness.

Weber-Fechner Law

• Sensation intensity relation to stimulus log ratio.

Isophonic Curves

• Representation of sound intensity and frequency for same loudness sensation.

Hearing Mechanism (Air Conduction)

• Mechanism description for hearing from outer to inner ear via ossicles.

Bone Anisotropy

• Resistance to mechanical stress varies with force's direction.

Fluid Continuity Equation

• Relation between flow rate and cross-sectional areas (in fluid dynamics).

Hagen-Poiseuille Law

• Equation relating volumetric flow rate, pressure gradient, and viscosity.

Lung Compliance Factors

• Factors determining lung compliance.
• Example: Tissue elastic recoil and surface tension

Surface Tension

• Work needed to increase a liquid's surface area

Atomic Force Microscopy Resolution

• Resolution limit for atomic-level imaging.

Sedimentation Constant

• Sedimentation velocity under unit acceleration.
• Units (Svedberg).

Electrophoretic Mobility

• Velocity of a particle in electric field.

This quiz covers essential physics topics including kinetic energy, force, momentum, and the electromagnetic spectrum. Test your understanding of these fundamental concepts and their applications in real-world scenarios. Ideal for students learning about energy and motion in physics.