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Definitions Competition Flashcards

1
Q

What is Acoustic Impedance?

A

The resistance a medium offers to the propagation of sound waves.

Formula: Z = ρ × speed of sound; Unit: kg/m²·s.

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2
Q

What is the Diffusion Coefficient?

A

A measure of how quickly molecules spread through a medium due to random thermal motion.

Unit: m²/s.

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3
Q

Define Pair Production.

A

A phenomenon where a high-energy photon transforms into an electron–positron pair when it passes near a nucleus.

Energy threshold: 1.022 MeV.

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4
Q

What is Fluorescence Lifetime?

A

The average time a molecule remains in an excited electronic state before emitting a photon and returning to the ground state.

Unit: seconds (commonly nanoseconds).

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5
Q

Define Action Potential.

A

A rapid, temporary change in the electrical membrane potential of a cell caused by the flow of ions through voltage-gated channels.

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6
Q

What is Effective Dose?

A

A radiation protection quantity that reflects the biological effect of radiation, accounting for the type of radiation and the sensitivity of the exposed tissues or organs.

Unit: Sievert (Sv).

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7
Q

What is the unit for Radiation Intensity?

A

Watts per square meter (W/m²) or Watts per square meter steridian (W/m²sr).

The SI unit for radiation intensity, or more specifically, radiant inten

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8
Q

What is the unit for Electrochemical Potential?

A

Volts (V).

Electrochemical potential is expressed in units of joules per mole (J/mo

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9
Q

What is the unit for Specific Capacity?

A

Joules per kilogram per Kelvin (J/kgK).

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10
Q

What is the unit for Mass Attenuation Coefficient?

A

Square meters per kilogram (m²/kg).

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11
Q

What is the unit for Compressibility?

A

Reciprocal pascal (Pa⁻¹), or 1 per pascal.

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12
Q

What is the unit for Entropy?

A

Joules per kelvin (J/K).

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13
Q

What is the unit for Permeability (magnetic)?

A

Henry per meter (H/m).

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14
Q

What is the unit for Radiation Weighting Factor?

A

Dimensionless.

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15
Q

Compare Film Dosimeter and Thermoluminescent Dosimeter (TLD).

A

Film Dosimeter:
* Uses photographic film
* Single-use
* Visual or densitometric readout
* Simple and inexpensive, but not very precise.

TLD:
* Stores energy from radiation
* Reusable
* More sensitive
* Provides precise numerical readings.

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16
Q

Compare Contact Thermography and Telethermography.

A

Contact Thermography:
* Uses physical sensors on skin
* High-resolution, localized measurements
* Requires skin contact.

Telethermography:
* Uses infrared camera
* Detects heat without contact
* Ideal for scanning large areas.

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17
Q

What does the Donnan Model describe?

A

Passive ion distribution across a membrane when impermeant ions are present, explaining equilibrium potential caused by trapped charges.

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18
Q

What is the Goldman–Hodgkin–Katz (GHK) Model?

A

Calculates membrane potential considering the permeability of several ions, reflecting dynamic, non-equilibrium steady-state conditions.

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19
Q

What is the Resting Membrane Potential?

A

The electrical potential difference across the cell membrane of a resting cell, typically about –70 millivolts.

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20
Q

What factors contribute to the Resting Membrane Potential?

A
  • Unequal distribution of ions (K⁺, Na⁺, Cl⁻)
  • Selective permeability of the membrane
  • Activity of the sodium-potassium pump.
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21
Q

What is the Reduced Eye Model?

A

A simplified representation of the human eye using a single convex lens to simulate the optical system.

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22
Q

What is the focal length of the Reduced Eye Model?

A

The Reduced Eye Model has a focal length of approximately 22.22 mm when considering the emmetropic eye, meaning an eye that can focus light from distant objects onto the retina. This simplifies the complex optics of the eye into a single refracting surface, making it easier to understand and model. About 17 mm.

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23
Q

Describe the function of a Gamma Camera.

A

Detects gamma photons from a radioactive tracer, converts photon impacts into light, and maps it into a visual image.

A Gamma Camera, also known as a Scintillation Camera or Anger Camera, is

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24
Q

What is the Working Principle of Atomic Force Microscope (AFM)?

A

The AFM operates by using a tiny, sharp tip attached to a cantilever to scan a surface and measure the forces between the tip and the sample. The tip’s interaction with the surface causes the cantilever to bend, and this bending is detected using a laser and a photodetector. A sharp tip attached to a flexible cantilever scans the surface, and atomic-scale forces cause deflection.

1. Tip and Cantilever: The AFM uses a very sharp tip, attached to a smal

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25
What are the modes of AFM?
* Contact * Tapping * Non-contact.
26
What is the Thermooptical Effect?
The refractive index of a material changes with temperature.
27
What is the Electrooptical Effect?
The refractive index of a material changes in response to an electric field.
28
29
What is the formula for the average kinetic energy of a gas molecule?
(1/2)mv² = (3/2)kT ## Footnote Formula booklet I.34, page 7
30
How does molecular mass affect gas speed at the same temperature?
Lighter molecules move faster; speed is inversely proportional to the square root of mass.
31
What is the formula for root-mean-square (rms) speed of gas molecules?
v = sqrt(3kT / m) ## Footnote Formula booklet I.34, page 7
32
What does the Arrhenius equation describe?
The temperature dependence of processes like defect formation or reaction rates.
33
What does the Boltzmann distribution tell us in atomic excitation?
The fraction of atoms in excited states at a given temperature.
34
What is the Boltzmann distribution formula for excitation?
n₂/n₁ = exp(–ΔE / kT) ## Footnote Formula booklet I.26, page 7
35
How do you calculate the energy of a photon from wavelength?
E = hc / λ ## Footnote Formula booklet, Light Emission
36
What units are needed to use E = hc / λ directly?
E in joules, λ in meters, h and c in SI units.
37
What is the formula for intensity (power density) of a laser beam?
J = P / A
38
What is Exposure Rate?
Rate of ionization produced by radiation in air; unit: C/kg·s or R/h.
39
What law describes radiative heat loss from a body?
Stefan–Boltzmann law ## Footnote P = σAT⁴ (Watts) Formula booklet, bottom page 8: M = σT⁴ (W per unit area)
40
What is the Stefan–Boltzmann formula for net power loss?
P = σA(T_skin⁴ – T_ambient⁴)
41
What is the maximum photon energy in an X-ray tube?
E = eU = hf ## Footnote Formula booklet: X-ray, page 4
42
How do you calculate the minimum X-ray wavelength?
λmin = hc / eU ## Footnote Formula booklet: X-ray, page 4
43
How do you find total power input to an X-ray tube?
P = U × I
44
How do you calculate the speed of an electron from accelerating voltage?
v = sqrt(2eU / m) | m: mass of an electron
45
What does Kirchhoff’s law state about emissivity and absorptivity?
Emissivity = absorptivity at thermal equilibrium ## Footnote This law applies to thermal radiation.
46
What is the Duane-Hunt law used to calculate?
Maximum photon energy in X-ray tube ## Footnote Formula: Emax = eU.
47
What does the Third law of thermodynamics state about entropy?
Entropy approaches zero as temperature approaches 0 K
48
What occurs during Compton scattering?
Photon scatters off an electron, losing energy and increasing wavelength
49
According to Kasha’s rule, from which state does fluorescence emission occur?
Lowest excited singlet state
50
What does Abbe’s principle relate the resolving power of optical instruments to?
Aperture and wavelength
51
What is the average lifetime of a radioisotope?
Mean time before decay of a radioactive nucleus ## Footnote Formula: τ = 1/λ = T/ln2, Unit: seconds (s)
52
What does Biot’s law describe?
Optical rotation of polarized light in optically active substances ## Footnote Formula: α=[α]lc, where [α] = specific rotation, l = path length, c = concentration; Unit: degrees.
53
What is equivalent dose in radiation?
Radiation dose accounting for biological effect ## Footnote Formula: H=D×wR, where wR = radiation weighting factor; Unit: sievert (Sv)
54
What is an optical resonator?
Structure that confines light by reflecting it back and forth (e.g., in lasers)
55
What is Stokes shift?
Difference in wavelength between absorption and emission maxima in fluorescence
56
What is viscoelasticity?
Property of materials that exhibit both viscous and elastic characteristics when deformed
57
What is viscosity?
Measure of a fluid’s resistance to flow ## Footnote Unit: Pascal-second (Pa·s)
58
What is the unit of radiant flux?
W (watt)
59
What is the unit of resolving power?
Dimensionless
60
What is the unit of refractive power?
Dioptre (D) = m^−1
61
What is the unit of optical density?
Dimensionless
62
What is receptor potential?
Graded change in membrane potential in sensory neurons in response to a stimulus ## Footnote No threshold, varies with stimulus strength.
63
What is action potential?
Rapid, all-or-none electrical impulse along neurons; constant amplitude, triggered once threshold is reached
64
What does Weber’s Law describe?
ΔI/I = k ## Footnote k is the constant ratio for detectable change.
65
What does Fechner’s Law state about sensation?
Sensation S is proportional to log(I)
66
What does Stevens’ Power Law express?
S = kI^n ## Footnote Sensation is a power function of intensity.
67
What is the average time a molecule stays in the excited state before emitting a photon?
Fluorescence lifetime ## Footnote Unit: seconds
68
What is K-electron capture?
A radioactive decay mode where a nucleus captures an inner K-shell electron.
69
What does EM: Relative depth dose (RDD) measure?
The dose at a particular depth relative to the dose at a reference depth. ## Footnote Unit: dimensionless
70
What is the definition of effective dose (ED)?
Dose adjusted for radiation type and tissue sensitivity. ## Footnote Unit: Sievert, Sv
71
What does EP: Exposure rate refer to?
Rate at which exposure occurs. ## Footnote Unit: C/kg·s or R/h
72
What is population inversion?
Condition where more particles occupy a higher energy state than a lower one, necessary for laser operation.
73
What is the piezoelectric effect?
Electric charge generation due to mechanical stress in certain crystals. ## Footnote Unit: C/m² or V/m
74
What does the Zeroth law of thermodynamics state?
If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
75
What is the diffusion coefficient (ED)?
Quantity characterizing the diffusion rate. ## Footnote Unit: m²/s
76
What is the unit for Ultrasound specific attenuation?
dB/(cm·MHz) | This is another name for specific damping (per the textbook). ## Footnote Ultrasound specific attenuation measures how much ultrasound energy is absorbed by tissue.
77
What is the unit for Radiant emittance?
W/m² ## Footnote Radiant emittance refers to the power emitted per unit area.
78
What is the unit for Half-value mass?
kg/m² ## Footnote Half-value mass indicates the mass required to reduce the intensity of radiation by half.
79
What unit is used to express Refractive power?
Diopter (D) = 1/m ## Footnote Refractive power indicates the ability of a lens to bend light.
80
What is the unit for Molar extinction coefficient?
L/(mol·cm) ## Footnote The unit for molar extinction coefficient (often represented by the Greek letter epsilon, ε) is M⁻¹ cm⁻¹ or L mol⁻¹ cm⁻¹. This unit arises from the Beer-Lambert Law (A = εcl), where A is absorbance, c is concentration (in M or mol/L), and l is path length (in cm). Since absorbance is dimensionless, the units of ε cancel out to leave M⁻¹ cm⁻¹.
81
What is the unit for Chemical potential?
The standard unit for chemical potential is joules per mole (J/mol), or equivalently, Gibbs free energy per mole, which is also expressed as Gibbs. ## Footnote Chemical potential represents the change in free energy when particles are added to a system.
82
What is the unit for Decay constant?
1/s ## Footnote Decay constant indicates the rate at which a radioactive substance decays, lambda
83
What is the unit for Tissue weighting factor?
Dimensionless ## Footnote Tissue weighting factor is used in radiation protection to account for the different sensitivities of various tissues to radiation.
84
What is a smectic liquid crystal?
A phase of liquid crystal in which the molecules are arranged in layers and can flow freely like a liquid within each layer. ## Footnote Molecules are typically oriented in the same direction.
85
Define circularly polarized light.
An electromagnetic wave where the electric field vector rotates in a circle around the direction of propagation, forming a helical pattern. ## Footnote It may be right- or left-handed.
86
What is the limiting wavelength of X-radiation?
The shortest wavelength X-ray that can be produced in an X-ray tube, resulting from full conversion of electron kinetic energy into a photon. ## Footnote λmin = hc / eU
87
Define entropy.
A thermodynamic quantity representing the disorder in a system or the number of microscopic configurations. ## Footnote Formula: S = k ln (Omega)
88
What is stationary flow?
Flow is steady in time (textbook definition) :( ## Footnote None
89
What is the Einthoven Triangle?
An imaginary equilateral triangle formed by the three limb leads (I, II, III) of an ECG, used to interpret electrical activity of the heart. | Einthoven's triangle is a theoretical concept in electrocardiography (EC ## Footnote None
90
Fill in the blank: A smectic liquid crystal allows molecules to flow freely like a liquid within each _______.
layer ## Footnote None
91
True or False: Circularly polarized light can only be right-handed.
False ## Footnote Circularly polarized light can be either right- or left-handed.
92
What is the unit for measuring entropy?
Joules per kelvin (J/K) ## Footnote None
93
What does the limiting wavelength λmin = hc / eU formula represent?
The relationship between the shortest wavelength X-ray produced and the kinetic energy of electrons. ## Footnote ( h ) is Planck's constant, ( c ) is the speed of light, ( e ) is the charge of an electron, and ( U ) is the voltage.
94
What is the formula for specific damping? State its units. | Can also be referred to a specific attentuation
Specific damping = α/(fx) | Specific damping is measured in dB/(cm MHz) ## Footnote Can't find this formula in formula booklet
95
We memorised a formula for reflectivity that makes use of damping (not specific damping!) It's not in the formula booklet :(
J=J0*R*10^(-damping/10) | J0: original intensity damping, alpha, is not specific damping. You must
96
What is the Beer–Lambert law?
The absorbance of a material that has only one absorbing species also depends on the pathlength and the concentration of the species, according to the Beer–Lambert law A=εcℓ ε is the molar absorption coefficient of that material; c is the molar concentration of those species; ℓ is the path length.
97
What is the limiting angle of vision?
Maximum angle at which an object can be seen clearly.
98
What unit is the mass attenuation coefficient measured in?
cm²/g
99
What does the linear attenuation coefficient describe?
How easily a material attenuates a beam of radiation per unit length.
100
What unit is the linear attenuation coefficient measured in?
cm⁻¹
101
What is the formula for the linear attenuation coefficient?
μ_m = μ / ρ | μ: linear attenuation coefficient, m^-1 μ_m: mass attenuation coeff
102
What is exposure in the context of radiation?
Charge produced per unit mass of air. | X=Δq/Δm
103
What units is exposure measured in?
Roentgen (R) or C/kg
104
What is specific resistance?
Electrical resistivity per unit length and cross-sectional area.
105
What unit is specific resistance measured in?
ohm·meter (Ω·m)
106
What is the formula for specific resistance?
R = ρ × (L / A) | ρ: resistivity of the material
107
What is loudness?
Perceived intensity of sound.
108
What unit is loudness measured in?
decibel (dB)
109
What is the formula for calculating loudness?
J_dB = 10 × log10(J/J0) ## Footnote Formula booklet, page 5, right column
110
What is population inversion?
More particles in excited state than in ground state — needed for laser action.
111
In population inversion, what condition must be met?
N2 > N1
112
Is exposure the same thing as absorbed dose?
Exposure does not describe the energy transferred to a given material. The absorbed dose measures the deposition of energy E which causes radiation damage in a given mass of material, such as tissue.
113
What is the formula for absorbed dose?
D=ΔE/Δm
114
What is dose rate?
The absorbed dose in an amount of time ## Footnote D=ΔE/ΔmΔt
115
What is the relationship between exposure and dose rate?
D = f0 * X | f_0: energy required to produce unit charge in the material, measured in ## Footnote Formula booklet, page 10, II.107

Biophysics (2 decks)

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