Therapeutic Use of Light Flashcards
(43 cards)
What is an Angstrom?
measurement of a wavelength
What is a nanometer?
measurement of a wavelength (billionths of a meter)
What is the electromagnetic spectrum?
range of all possible frequencies of electromagnetic radiation.
What is the inverse square law?
intensity of the waves from a point source varies inversely with the square of the distance from the source. I = 1/D^2
What is the cosine law?
optimal radiation of a surface occurs when the source of the radiation is at right angles to the irradiated surface.
What are the properties of light?
- Wavelength
- frequency
- reflection
- refraction
- absorption
- Photon
- Coherence
- Divergence
- monochromaticity
What is wavelength?
distance between the beginning and end of a single wave cycle.
Each wavelength of visible light has its own specific color
What is frequency?
- inversely proportional to wavelength
- higher frequencies are absorbed more superficially
- usually measured in Hz equal to one cycle per second
What is reflection?
bouncing back of light or sound waves from a surface that they strike
What is refraction?
Change in direction of a sound or light wave when it passes from one medium of different density to another
What is absorption?
substance’s ability to take in light or radiant energy.
What is a photon?
- light as it travels in bundles.
- unit of energy of a ray of light
What is monochromaticity?
all photons have a single wavelength = one color
What is coherence?
- way the wavelength travels;
- all photons travel in the same phase and direction producing a precise parallel beam of light
What is divergence?
-relative parallelism of the beam, minimal divergence over distance = collimated (parallel) or concentrated beam.
What are the factors that influence radiation intensity?
- the strength of the energy output of the source
- the distance of the irradiated area from the source
- the angle of the rays striking the area
- the size of the irradiated area
What are the sources of UV?
- The sun (heliotherapy)- near ultraviolet
- Hot quartz lamps- mercury vapor arc lamp has 2 tungsten filaments; produces complete UV spectrum
- cold quartz lamps- produces energy in the far or short UV range; primarily used for bacterial effect b/c will produce erythema
What is the measurement of UV the sun
2900-4000 angstroms
290-400 nm
What is the measurement of cold quartz?
2540 angstroms
254 nm
What is the range of the UV irradiation?
3900-1800 angstrom
390-180 nm
*divided into near UV and far UV
What is the range of the near UV?
3900-2900 A
390-290 nm
continuous with visible light
What is the range of far UV?
2900 to 1800 A
290 to 180 nm
*less visible light
What are the physiological effects of UV irradiation?
- erythema production: radiant energy in wavelengths of 2400-3200 A, 240-320 nm, produces a local erythema of the skin, caused by histological changes.
- Pigmentation of the skin due to deposits of melanin in the basal cells of the skin; it results primarily from wavelengths of 2900-3200 A, 290-320 nm
- Thickening of the horny layers of the skin
- possible carcinogenic effects on the skin
- Metabolic effect: production of vitamin D enhanced –> promotes anabolism of calcium and retention of phosphorus
- Bacterial effects: wavelengths of 2640 A are most effective–> produced by cold quartz lamp
- Systemic physiological effects occur with full body exposure, including temporary drop in blood pressure due to peripheral vasodilation and slight increase in muscle tone.
What are the indications for UV?
- diagnostic, to detect dead or deviatalized teeth and to detect ringworm infestations of the skin.
- dermatitis, including alopecia, herpes zoster, ringworm, acne.
- Surface infections within wounds and decubitis ulcers
- Osteomyelitis
- Psoriasis
