Biophysics Questions and Answers

Biophysics Questions and Answers

• Absolute Error Reduction: Measuring radioactive decay for four times as long, while maintaining constant activity, reduces the absolute error to one-quarter of its initial value.

• Non-SI Base Unit: Weight is not an SI base unit. SI base units include speed, luminous intensity, temperature.

• Stochastic Biological Effects: These effects are inheritable and their frequency of occurrence increases with dose. Their threshold dose varies depending on ionizing radiation type.

• Light Beam Refraction: The most significant change in light beam direction within the human eye occurs at the border between the lens and the vitreous fluid, not entry into the cornea.

• Viscous Liquid Velocity: Volumetric velocity is directly proportional to the pressure difference.

• Osmosis Pressure: Osmosis pressure equals the partial pressure of the solvent. Sound source approaching a detector results in detected frequency increase. Non-Newtonian fluids are one example of ideal fluids. With Stokes' law, the diffusion constant inversely relates to the medium’s viscosity.

• Blood Dilution Measurement: Isotopes like ⁵¹Cr are used to measure blood dilution volume, not ¹²³I, ⁹⁹mTc, or ¹³¹I.

• Light Refraction and Notes: If light passes from a higher refractive index medium to a lower refractive index, the refractive angle is less than the angle of incidence; higher notes have slower speeds than lower notes. Thermography uses electromagnetic radiation. Mediated diffusion is faster than simple diffusion.

• Radioactive Decay Constant: A radioactive isotope with a 1-second half-life has a decay constant approaching 0.7/s.

• EEG Waves During Rest: Alpha waves are emitted by a resting brain.

• Biconcave Lens: A biconcave lens acts as a spray lens when the radii of curvature are equal and the lens has a lower refractive index than the surrounding medium.

• Brain Imaging Resolution: Computed Tomography (CT) imaging significantly worsens brain image resolution due to absorption by the skull bone.

• Laplace Law: Laplace Law describes the tension created by pressure in the wall of a circular pipe.

• Blood Pressure Change: Blood pressure in the brain typically decreases after a sudden change in posture to a standing position.

• Laminar Blood Flow: If the radius of a vessel increases by 19%, blood's volume flow rate increases by about 68.89% (3x the radius increase in flow).

• Imaging Methods: CT and PET use ionizing radiation in image creation.

• Dark-Adapted Eye: The dark-adapted eye is more sensitive than the light-adapted one, but visual acuity is poorer. Visual adaptation from dark to light occurs within minutes.

• Light Wave Interference: Persistent interference occurs between light waves that are coherent and have a constant phase difference.

• SI Unit for Decay Constant: The SI unit for the decay constant is reciprocal time (1/s).

• Korotkov Noise: Korotkov noise occurs during the transition of blood flow from turbulent to laminar within the artery during blood pressure measurement.

• Scatter Lens Image: If a straight object is within a scatter lens' focal length, the image is virtual and upright.

• Biological Effect of Ionizing Radiation: Alpha radiation, of the same energy transfer, has a larger biological effect than other types of radiation (3 MeV x-rays, 3 MeV neutrons, and 3 MeV protons).

• Ultracentrifuging: Heavier particles settle faster during ultracentrifuging. A particle with a higher density settles faster. And Lower friction coefficient results in a faster movement speed.

• Beta Decay Positron: Positron emission in beta decay decreases the mass number by one.

• Effective Half-Life: An administered radioactive isotope's effective half-life is always less than its biological half-life.

• Alpha Particles: Alpha particles are helium nuclei (doubly ionized helium atoms).

• EEG Wave Amplitude: Beta waves' amplitude typically ranges between 50-100µV.

• Radioactive Decay Percentage: 75% of the 10-minute half life isotope 13N has decayed after 20 minutes.

• Radioactive Decay of 14N: After 40 minutes, approximately 6.25% of 14N isotope, with a 10-minute half-life, remains undecayed.

• Lens System Refractive Power: The refractive power of two thin lenses in contact is the sum of their individual refractive powers.

• Radioactive Source Activity: The activity of a radioactive source is the number of radioactive decays per second, not alpha particles emitted, total energy, or ionizing effect.

• Stokes Law: The Stokes Law describes the force of resistance experienced by a spherical body moving in a viscous liquid.

• Non-Electromagnetic Imaging: Echoencephalography, not radioactive tracing, thermography, or PET, is an imaging method that does not utilize electromagnetic radiation to create images.

• Diffusion Constant SI Unit: The SI unit for the diffusion constant is kg/ms.

• Refraction and Media Properties: The degree of refraction at the interface of two media depends on the speeds of light in each and the relative refractive index of one medium to another.

• Light Wave Interaction: Two meeting light waves can lead to persistent interference if they're coherent and have a constant phase difference.

• Lens Image: If a real, upright object is beyond a collecting lens' focal length, the formed image is real and inverted (reversed).

• Coil Diathermy Frequency: 2570 MHz.

• Ultrasound Frequency: 2-18 MHz.

• Ideal Fluid Pressure Variation: When the diameter of an ideal fluid-filled pipe increases, the pressure decreases; when it decreases, pressure increases.

• Diffusion Constant Dependence: The diffusion constant (D) depends on temperature, the medium's characteristics (viscosity), and the shape of the diffusing particle.

• Cancerous Tumor Imaging: MRI is an imaging technique better than CT, gamma camera, or SPECT for accurately locating cancerous tumors.

• Braking Radiation: Braking radiation's minimum wavelength depends only on the target material. its power is related to the accelerating voltage. The total energy is less than the electron beam's energy. It contains a spectrum not sharply distinct peaks.

• Patch-Clamp Technique: The patch-clamp technique maintains the membrane voltage at a predetermined value, enabling researchers to study ion channel activity across cell membranes.

• EEG Wave Frequency: Delta waves have a frequency in the 4-7 Hz range.

• Hemolysis-Causing Solution: A hypotonic infusion solution causes hemolysis.

• ECG Signal Amplitude: The QRS complex of a two-lead ECG signal typically has a peak magnitude of 1-2 mV, not 2-3 mA or 20-25 Watt.

• Lambert Law: The Lambert Law refers to the decrease in light intensity as it passes through a material, which is dependent on the material's thickness.

• Blood Pressure Location: Blood pressure is highest in the heart and lowest in parts of the feet, furthest from the heart, in a person who is standing upright.

• Viscosity and Volumetric Rate: The volumetric rate of a viscous liquid is inversely proportional to its viscosity, not proportional.

• Isotonic NaCl Concentration: The concentration of sodium in isotonic NaCl saline is 0.9%.

• Effective Dose Unit: The unit for effective dose is J/kg.

• Uncertainty in Measurements (Quantities): The empirical standard deviation decreases as the number of measurements increases. The error in the mean decreases.

• Non-SI Basic Quantity: Weight is not an official SI basic quantity. Speed, luminous intensity, and temperature are.

• Non-official SI Unit: Fermi, rad, Kev, and are not official SI units.

• Dark-Adapted Eye Limitations: A dark-adapted eye is the most sensitive, but its visual acuity is poor; color perception is diminished.

• Mechanical Energy: Mechanical energy is equivalent in both cases; the location or speed of an object does not affect its mechanical energy.

• Photoelectron Energy: The energy of photoelectrons depends on the light's frequency, not intensity. Higher notes have less penetration power than lower ones.

• Inhaled Isotope Decay: The percentage of the inhaled ¹¹C (20-minute half-life) isotope that remains undecayed after one hour is 12.5%.

• Diffusion Constant Properties: The diffusion constant (D) is proportional to temperature but inverse by viscosity of the medium, not proportional to the mass of the diffusing particle.

• Electron Wavelength Calculation: Determining an electron's wavelength requires knowledge of its kinetic energy.

• Coherent Interference: Two light waves cause persistent interference only when they are coherent (maintain a constant phase difference).

• Decay Constant: The decay constant is inversely proportional to the half-life.

• 131I Activity: A typical activity of ¹³¹I used in thyroid tests is 2 mCi (megacuries).

• Beta Particles: Beta particles are high-energy electrons.

• Voltage Clamp Technique: A voltage clamp maintains a set membrane potential.

• EEG Wave Amplitude: Delta waves are characterized by amplitudes below 20 µV. The amplitude of the EEG waves can vary.

• Error of Difference of Quantities: The absolute error of the difference between quantities is the square root of the sum of their squared absolute errors.

• Radioactive Decay Constant and Half-Life: Decay constant is inversely proportional to half-life.

• Microwave Frequency: 2.54 GHz is the microwave frequency.

• Infusion Solution and Plasmolysis: A hypertonic solution causes plasmolysis.

• Irradiation Dose Unit: The SI unit for the irradiation dose is the Gray (Gy).

• Capacitor Field Diathermy: 2.570 MHz

• Real Object Image from a Lens: A real, upright object located within the focal point of a collector lens generates an apparent, erect image outside the lens.