University Medical Physics and Physical Chemistry Study Notes

Dissociation Coefficient ( $\alpha$ ): Defined as the ratio of dissociated molecules to the total number of dissolved molecules. It is a dimensionless, derived quantity. * Strong Electrolytes: $\alpha = 1$ (fully dissociated). * Weak Electrolytes: $\alpha < 1$ (partially dissociated).
Conductivity factors: Depends on the nature of the electrolyte, $\alpha$ , temperature ( $T$ ), and the mobility ( $\mu$ ) of cations and anions.
Ion Mobility: Numerically equal to the average velocity of an ion in a unit electric field. In solutions, it is inversely proportional to medium viscosity ( $\eta$ ) and ion radius ( $r$ ).

Expansion Types: Linear ( $l = l_0(1 + \alpha \Delta t)$ ), surface ( $S = S_0(1 + \beta \Delta t)$ ), and volume ( $V = V_0(1 + \gamma \Delta t)$ ).
Coefficients: Units are $K^{-1}$ . For isotropic bodies, $\gamma \approx 3\alpha$ .
Liquid Density: Generally decreases as temperature increases; $\rho = \frac{\rho_0}{1 + \gamma \Delta t}$ .
Water Anomaly: Between $0\,^{\circ}\text{C}$ and $4\,^{\circ}\text{C}$ , water contracts ( $V$ decreases, $\rho$ increases). It reaches maximum density ( $1000\,kg/m^3$ ) at $4\,^{\circ}\text{C}$ .

Principles: Based on the Zero-th Principle of Thermodynamics (thermal equilibrium). Thermometers require a thermometric substance and a physical property that varies linearly with $T$ .
Calibration: Includes choosing benchmark temperatures (e.g., triple point of water) and dividing intervals into units (degrees).
Temperature Scales: * Kelvin ( $K$ ): Absolute scale; fixed at the triple point ( $273.16\,K$ ). * Celsius ( $^{\circ}\text{C}$ ): Linear relationship with Kelvin; defined by melting ice ( $0\,^{\circ}\text{C}$ ) and boiling water ( $100\,^{\circ}\text{C}$ ).
Mercury ( $Hg$ ): Preferred because it is opaque, does not wet glass, is a good heat conductor, and remains liquid from $-38.8\,^{\circ}\text{C}$ to $357\,^{\circ}\text{C}$ .
Pharmaceutical Storage: * Cold: $2 - 8\,^{\circ}\text{C}$ . * Cool place: $8 - 15\,^{\circ}\text{C}$ . * Normal temperature: $15 - 25\,^{\circ}\text{C}$ .
Accelerated Aging: Stability tests for drugs using elevated temperatures (e.g., $25 - 50\,^{\circ}\text{C}$ or $50 - 70\,^{\circ}\text{C}$ ).

Diffusion: Spontaneous transport of molecules caused by random agitation to reach equilibrium; described by Fick's Laws. The diffusion coefficient ( $D$ ) depends on nature, $T$ , viscosity ( $\eta$ ), and particle size.
Osmosis: Passage of solvent through a semipermeable membrane toward a higher concentration solution.
Osmotic Pressure ( $\pi$ ): Pressure exerted by solute molecules; Van’t Hoff Law states $\pi V = nRT$ .
Red Blood Cells (RBCs) in Solutions: * Isotonic: $0.9\%\,NaCl$ ( $9\,g/dm^3$ ) or $4.7\%\,Glucose$ ( $47\,g/dm^3$ ); cells maintain shape. * Hypotonic: Cells swell (turgescence) and may suffer hemolysis. * Hypertonic: Cells shrink (plasmolysis).

Ideal Gas: Characterized by disordered motion, elastic collisions, and negligible molecular volume. * Boyle-Mariotte (Isotherm): $p \cdot V = \text{constant}$ . * Gay-Lussac (Isobar): $\frac{V}{T} = \text{constant}$ . * Charles (Isochoric): $\frac{p}{T} = \text{constant}$ .
Dalton's Law: Total pressure of a gas mixture equals the sum of partial pressures.
Real Gases: Van der Waals equation $(p + \frac{a}{V^2})(V - b) = nRT$ introduces internal pressure ( $a$ ) and covolume ( $b$ ).
Andrews Isotherms: At temperatures above the critical point ( $31\,^{\circ}\text{C}$ for $CO_2$ ), gases cannot be liquefied by pressure alone.

Coulomb's Law: $F = \frac{1}{4\pi\varepsilon_0 \varepsilon_r} \frac{q_1 q_2}{r^2}$ . Interaction decreases in media with high relative permittivity ( $\varepsilon_r$ ).
Electric Field ( $E$ ): Vector quantity characterizing the force on a charge ( $E = \frac{F}{q}$ ).
Electric Potential ( $V$ ): Scalar quantity measured in Volts ( $V$ ).
Electric Dipole: Two equal and opposite charges at distance $l$ . Dipole moment $p = q \cdot l$ (unit: $C \cdot m$ ).
Molecules: Water is a permanent dipole with a high dielectric constant. Non-polar molecules can become induced dipoles in an external field.

Physiological Limits: Max safe current is $10\,mA$ (AC) and $50\,mA$ (DC). Fibrillation (desynchronized heart activity) occurs at low intensities through the cardiac region.
Joule Effect: Heating of a conductor; $Q = R I^2 t$ . Power $P = U \cdot I$ .
Superconductivity: Total loss of electrical resistance below a critical temperature ( $T_c$ ), useful in MRI and particle accelerators.

Electric Field: Charged particles undergo parabolic motion; acceleration $a = \frac{q E}{m}$ .
Magnetic Field (Lorentz Force): $F = q(\mathbf{v} \times \mathbf{B})$ . If $\mathbf{v} \perp \mathbf{B}$ , the particle follows a circular path with radius $r = \frac{m v}{q B}$ and frequency $f = \frac{q B}{2\pi m}$ .
Mass Spectrograph: Separates isotopes based on their specific charge ( $q/m$ ) or "speed filter" ( $v = \frac{E}{B}$ ).

Visible Light: Range $400 - 750\,nm$ . Eye sensitivity is maximum at $550\,nm$ (green).
Units: Luminous intensity (candela, $cd$ ), Luminous flux (lumen, $lm$ ).
Refraction: $n_1 \sin(i) = n_2 \sin(r)$ . Absolute refractive index $n = \frac{c}{v}$ .
Total Internal Reflection: Occurs when moving from a denser to a less dense medium at an angle greater than the limiting angle; used in endoscopes and optical fibers.
Dispersion: Dependence of $n$ on wavelength (violet deviates most in normal dispersion).

Converging Lenses: Can form real or virtual images; used for magnification.
Diverging Lenses: Always form virtual, upright, and smaller images.
Convergence ( $C$ ): Measured in diopters ( $m^{-1}$ ); $C = \frac{1}{f}$ .
Microscope: Combines a converging objective (forms real, magnified, inverted image) and eyepiece (forms final virtual, magnified image).

Absorption Laws: Lambert-Bouguère Law ( $I = I_0 e^{-kx}$ ) and Beer's Law (depends on concentration). Optical density is additive.
Polarization Methods: Reflection (Brewster Law: $\tan(i_B) = n$ ), refraction, double refraction (birefringence), and dichroism (Tourmaline, Herapatit).
Malus’s Law: $I = I_0 \cos^2(\alpha)$ .
Biot’s Law (Rotatory Polarization): $\alpha = [a] \cdot l \cdot c$ . Used to measure sugar content (polarimetric dosage).

Classification: * Ionizing: X-rays, gamma, $\alpha$ , $\beta$ . Can damage DNA. * Non-ionizing: UV, IR, visible, microwaves, radio waves.
X-rays (RX): Discovered by Röentgen in 1895. Produced in a Coolidge tube. * Braking Radiation (Bremsstrahlung): Continuous spectrum from electron deceleration. * Characteristic Radiation: Line spectrum specific to anticathode material (Moseley's Law).
Attenuation: Follows exponential law $I = I_0 e^{-\mu x}$ . High-density metals like lead ( $Pb$ ) are effective absorbers.

Nucleus Factors: Contains protons ( $p^+$ ) and neutrons ( $n^0$ ). Stability depends on short-range internuclear forces.
Isotopes: Same atomic number ( $Z$ ), different mass number ( $A$ ).
Decay Types: * $\alpha$ : Helium nuclei ( ${}_2^4 He$ ); high ionization, low penetration. * $\beta$ : Electron flows; higher penetration. * $\gamma$ : Electromagnetic waves; highest penetration, accompanies $\alpha$ / $\beta$ emission.