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| Question | Answer |
| Examples of Non-ionizing Electromagnetic radiation: | Visible Light Ultraviolet Light (UV) Infrared radiation (IR) Micro waves (MW) Radio Waves |
| Visible Light - Where does the range lie? Wavelength between ? nm and ? nm Photon energies between ? eV and ? eV | Lies between UV and IR Wavelength between 380 nm and 760 nm Photon energies between 3 eV and 6 eV |
| Wave-particle Duality: Electromagnetic radiation exhibits properties of; 1.? 2.? 3.? | Electromagnetic radiation exhibits properties of; 1.Waves (geometrical and wave optics) 2.Particles - Photons (Quantum optics) 3.Planck's formula connects particle amd wave properties of light. "Light has a dual life, as a wave and as a particle" |
| The visible spectrum: Blue light vs Red light ?nm Wavelength? Frequency? Energy? | Blue (488nm); Short λ, High f, High En >Blue 2x energy than red Red (650nm); Long λ, Low f, Low En Photon (Particle) as a wave packet of energy |
| Wave optics Standard equation | λ = cT = c/v Wavelength = Speed of light x wave period = Speed of light / Freq of radiation |
| Quantum Optics (Planck's forumla) | Energy E of light quanta (photon) is proportional to its frequency v, and inversely proportional to its wavelength λ (Planck's Formula): E = h v = hc / λ |
| Planck's Constant | h = 6.626 x 10(-34) J.s |
| Dominance of wave or particle properties: Low Energy? High Energy? | Low Energy electromagnetic radiation (low f, long λ) exhibits ~wave~ properties: Reflection Refraction Diffraction Interference Polarization |
| Dominance of wave or particle properties: High Energy? | High Energy electromagnetic radiation (High f, short λ) exhibits "particle" properties; Photoelectric effect Compton scattering Pair production |
| Nature of light: Light is a transverse electromagnetic wave, consisting of two variable fields: 1.? 2.? 3.? | 1. Electric Field (With Intensity E>) 2.Magnetic Field (With Intensity H>) Two Fields propagate simultaneously with the speed of light c (for a particular medium) |
| Electromagnetic Wave; Describe 1.? 2.? | Electric and magnetic fields are vectors - i.e. they have both magnitude and direction; Fields are perpendicular to the direction of propagation |
| Speed of light (c) Determined by? Speed of light in vacuum (c) is? | Determined by the electric (electric permittivity) and magnetic (magnetic permeability) properties of the medium; Speed of light in vacuum (c) is 300,000 km/s |
| Optical density of a medium: Characterized by? | Characterized by "absolute" index of refraction (n); n - a number describes how light, or any other radiation, propagates through optical medium; n is the ratio of speed of light in vacuum (c) to the speed of light substance (v) n = c/v -For vacuum (by definition) n = 1 -For air n ~ 1 - for all other substances n > 1 |
| Definition of reflection; 1.? 2.? | Change of direction of light propagation at the interface between two media with different optical density; Reflected light does not pass into the second medium. |
| Laws of reflection 1st Law | Incident ray* and reflected ray, as well as the perpendicular at the point of incidence, lie in the same plane. |
| Laws of reflection 2nd Law | The angle of the incident ray (α) is equal to the angle of the reflected ray (β) |
| Definition - Incident Ray | Narrow beam of light |
| What does this Illustrate? | Law of reflection; α = β |
| Types of reflection; S? | Specular - Reflection from a smooth surface (surface irregularities are smaller than λ) Law of reflection is valid |
| Types of reflection; D? | Diffuse - reflection from a rough surface (irregularities are of the order λ or bigger) Law of reflection NOT valid |
| Definition - Refraction of light? | The change of direction of propagation of light at the interface between two media with different optical density. Refracted light passes from first medium to the second. |
| Laws of Refraction 1st Law? | Incident ray and refracted ray, as well as the perpendicular at the point of incidence, all lie in the same place. |
| Laws of Refraction 2nd Law? | Ratio of the sines of the angle of incidence (α) and refraction (y) is equivalent to the ratio of light velocities in the two media (Snell's Law) |
| Sin? Sin | Illustration of refraction laws Sin a/Sin y = C1/C2 |
| Refraction; Relation between α and y | If the first medium is less optically dense (lower index of refraction) than the second medium, the angle of incidence is larger than the angle of refraction α > y If the first medium is optically denser (higher index of refraction) than the second medium, the angle of incidence is smaller than the angle of refraction. α<y |
| Read<< TIR - The refracted ray is actually reflected because it returns into the first medium - a total internal reflection. | |
| Conditions for Total Internal Reflection; 1st 2nd Result | 1st - Light must pass from optically higher-density medium to optically lower-density medium. 2nd - Angle of incidence should be larger than the critical angle Result - Light is reflected back into the incident medium |
| Endoscope | Optical device for examinations of hollow body organs (stomach, bladder, colon, duodenum) With two optical fiber cables - One for illumination, one for image capture and delivery to monitor. |
| Describe Optical Fiber Cables Built? Optical Density? Light Beams incidence Signal | Built by great number of glass fibers; Fiber core is covered by glass layer of lower optical density For light beams incident to glass fibers at angles larger than the critical angle, a TIR occur Signal will be trapped inside and transmitted along the length of the fiber. |
| Medical examination using specular reflection (Forehead reflector) Light reflects onto the concave surface of the reflector and is focused onto an area of interest. | |
| Opthalmoscopy (Funduscopy/Fundoscopy) Describe How is it used? Types | Instrument for examination of eye's fundus (changes in the colour or pigment of the fundus, changes in the retinal blood vessels, abnormalities in the macula lutea) Light is shone into the patients eyes and the reflection of the retina is observed; Two major types; Direct - directly produced image Indirect - Indirectly producing image |
| Direct Ophthalmoscopy How? Where image forms? Forms? Image? Magnification? | Hand-held device Image forms directly on the retina Central retina area Image - Real or virtual Magnification ~ 15 x |
| Indirect Ophthalmoscopy How? Field of view? Magnification? | Image formed by a hand-held condensing lens Much wider field of view Less magnification ~ 2x - 5x |
| Diabetic retinal screening Why? | Higher risk of micro aneurysms and hemorrhages |
| Light absorption Describe? (Photons) | When light passes through a substance, part of the incident photons loose energy - the light is absorbed. The photons transfer their energy to the substance, increasing internal energy. |
| Law of light absorption | Transmission of radiant flux Ψ of incident light, decreases by exponential decay law /\ Ψ and Ψ0 - radiant flux (intensity) of the incident and the transmitted light, unit [W/m2] α - Linear absorption coefficient of the medium, unit [m-1] d - Thickness of tranversed medium, unit [m] |
| Absorption Spectrum | The dependence of linear absorption coefficient α on light wavelength λ is referred to as absorption spectrum. |
| Beer-Lambert-Bouguer Law | For body fluids, the absorption coefficient α is proportional to the molar concentration c of the dissolved substance: /\ ɛ - Molar absorptivity (molar extinction coefficient), depending on λ, unit [m2/mol] c - Molar concentration, unit [mol/m3] |
| Main absorbing components of tissues? M? H? W? | Melanin (Skin, hair, moles) - Absorption in visible and near IR light (400nm - 1000nm) Hemoglobin (blood) - Absorbs highly in UV & blue and green light of visible spectrum Water (in tissues) - Transparent to visible light, strong absorption of UV light below 300nm and of IR over 1300nm. |
| Laboratory methods based on light absorption: P? S? | Photocolorimetry - analysis of body fluids by attenuation measurement of coloured light. Spectrophotometry - An improved photocolorimetry method for analysis of body fluids by attenuation measurement of light of precise wavelength. |
| Pulse Oximetry What does it measure? Location? Source? Detects? Calculates? | To measure the oxygen level (saturation) in the blood; Probe (clip-like device), placed on finger or ear lobe. Source with two different types of light - IR and Red Detector - for transmitted light through the finger/ear lobe Microprocessor - Compares and calculates the differences in oxygen-rich (Hbo2) vs. oxygen-poor (Hb) Hemoglobin |
| Pulse Oximetry Operation How they absorb differently? Ratio? | Deoxygenated blood (Hb) absorbs light differently than oxygenated blood (HbO2), especially at 660 nm (red) and 920 nm (IR) Ratio of the difference of absorption at 660 nm vs 920nm is an indication of blood oxygenation. |
| Sebumeter Method for? Procedure? Whats measured? Result Units? | Method for direct measurement of skin lipid secretion (sebrum) of face, scalp, hair; Skin type Procedure: 0.1 mm transparent tape makes contact with the skin for 30s The transparency is measured by a light source and results in [ug/cm2] |
| Light Scattering How interacts? Photon Transfer + How is light scattering Determined? General Definition | Light interacts with systems of much smaller sizes (atoms and molecules); Photons transfer part of their energy to electrons in a substance, which vibrate and in turn emit new photons (light). Scattering is determined by particle size and observation. Light would be scattered, if the propagating medium contains small optical non-homogeneities, i.e particles with optical density different from the bulk medium. |
| Turbidimetry & Nephelometry Used for? Optical Properties? | For analysis of dispersed media/colloids (proteins, nucleic acids, viruses, bacteria) Optical properties of the sample (absorption, transmission, scattering) depend on the size of dispersed particles. |
| Turbidimetry Measures? Using? Concentration? Clinical Applications? | Measuring transmitted light and calculating the amount of absorbed light Using light spectrophotometer Concentration of particles in suspension dependent on their number and size Clinical Applications for determining of; total protein in biological fluids (urine, CSF) Amylase and lipase activity (starch or triglycerides as substrate |
| Nephelometry Measuring? Using? Amount? Clinical Applications? | Measuring scattered light Using light spectrophotometer with forward scattered detection or at angle (90, 70 or 37 degree) of maximal scattered light Amount of scattered light depends on the size and number of particles. Clinical Applications - For determination of: Immunoglobulins (total,IgG,IgE,IgM,IgA) Individual serum proteins - hemoglobin, albumin. |
| UV Rays: UV Range? UV rays in medicine, range? Wavelength compared to visible light? Photons compared to visible light? | UV range: 10nm - 400nm (Visible range:380nm - 760nm) UV rays in the 200nm - 380nm range are used in medicine UV rays have shorter Wavelength than visible light UV photons have higher energy than photons of visible light |
| UV Bands UV A UV B UV C | UV A (Aging,Allergy) ~ 315 nm - 380 nm UV B (Burn) ~ 280 nm - 315 nm UV C (Bacterial CELL) ~ 200nm - 280nm |
| Effects of UV Rays UVA UVB UVC | UVA - Effects of metabolism UVB - Photochemical effects UVC - Bactericide effects |
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