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Questions and Answers
What is the application of photocoagulation in medicine?
What is the application of photocoagulation in medicine?
What is the purpose of using IR absorbing filters in endoscopes?
What is the purpose of using IR absorbing filters in endoscopes?
What is the principle behind the working of endoscopes?
What is the principle behind the working of endoscopes?
What is the wavelength range of visible light?
What is the wavelength range of visible light?
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What is the application of transillumination in medicine?
What is the application of transillumination in medicine?
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What is the energy of UV photons compared to visible photons?
What is the energy of UV photons compared to visible photons?
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What is the effect of UV light on the skin?
What is the effect of UV light on the skin?
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What is the application of phototherapy in medicine?
What is the application of phototherapy in medicine?
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What is the main cause of skin cancer in humans?
What is the main cause of skin cancer in humans?
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What is the property of light that allows it to be used in medicine to heat tissues?
What is the property of light that allows it to be used in medicine to heat tissues?
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What is the term for the ratio of the speed of light in a vacuum to its speed in a given material?
What is the term for the ratio of the speed of light in a vacuum to its speed in a given material?
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What is the process by which an excited atom emits a photon and falls to a lower energy state?
What is the process by which an excited atom emits a photon and falls to a lower energy state?
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What is the type of laser that produces a high-intensity beam of light in a very short pulse?
What is the type of laser that produces a high-intensity beam of light in a very short pulse?
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What is the material used in the first laser produced by T.H. Maiman?
What is the material used in the first laser produced by T.H. Maiman?
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What is the wavelength of light emitted by a Ruby laser?
What is the wavelength of light emitted by a Ruby laser?
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What is the reason for the color of the Ruby crystal?
What is the reason for the color of the Ruby crystal?
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What is the term for the property of light that allows it to be focused to a very small spot?
What is the term for the property of light that allows it to be focused to a very small spot?
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What is the primary use of lasers in medicine?
What is the primary use of lasers in medicine?
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What is the effect of directing laser energy to human tissue?
What is the effect of directing laser energy to human tissue?
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Study Notes
Light in Medicine
Properties of Light
- Light changes speed when it goes from one material to another
- The ratio of the speed of light in a vacuum to its speed in a given material is called the index of refraction
- Light behaves both as a wave and as a particle
- As a wave, it produces interference and diffraction, which are of minor importance in medicine
- As a particle, it can be absorbed by a single molecule, and when absorbed, its energy is released in various ways
Heating Effect of Light
- When light is absorbed, its energy generally appears as heat
- This property is the basis for the use of IR light to heat tissues in medicine
- This property is known as fluorescence
Reflection of Light
- Light is reflected to some extent from all surfaces (e.g., endoscope)
- Reflection of light is used in medicine for imaging and diagnosis
Light Amplification by Stimulated Emission of Radiation (Laser)
Einstein's Theory
- In 1917, Einstein postulated that incident photons of energies exactly equal to the energy that an excited atom must eject if it falls to its lower energy state
- These incident photons stimulate the excited atom to fall to its lower state and release a photon in phase with the incident photon
Types of Lasers
- Pulse laser (e.g., ruby laser, semiconductor laser, glass laser)
- Continuous wave laser (e.g., neon-helium laser, argon laser)
Ruby Laser
- In 1960, T.H. Maiman produced a laser beam from a ruby crystal
- The active material in the ruby is the chromium ions
- Ruby laser is used in medicine for various applications, including eye surgery and skin treatments
Laser in Medicine
- Lasers are used in medicine primarily to deliver energy to tissue
- The laser wavelength used should be strongly absorbed by tissue
- Short wavelengths (400-600 nm) are always absorbed better than long wavelengths (700 nm)
- Laser energy directed to human tissue causes a rapid rise in temperature and can destroy the tissue
- The amount of damage to living tissue depends on the time the tissue is exposed to increased temperature
Applications of Laser in Medicine
- Used by surgeons for the painless removal of eye tumors
- Used as a "bloodless knife" in surgery
- Repairing retinal tears or holes that develop prior to retinal detachment (photocoagulation)
- Treatment of diabetic retinography (photocoagulation)
- Used in medical research for special three-dimensional imaging called holography
Application of Visible Light in Medicine
Curved Surfaces
- Curved lenses (convex, concave, and cylindrical) are used in medicine
- Curved mirrors are used in ophthalmoscope, otoscope, and other medical instruments
Endoscopes
- Endoscopes are used for viewing internal body cavities
- Based on the principle of total internal reflection
- Endoscopes are supplied with IR-absorbing filters to minimize tissue heating
Transillumination
- It is the transmission of light through the tissues of the body
- Used clinically in the detection of:
- Hydrocephalus (water-head) in infants
- Pneumothorax (collapsed lung) in infants
- Sinuses
- Breasts
- Gums
- Testes
Phototherapy
- Premature infants recover from jaundice when they are exposed to visible light
Microscopy
- The smallest objects that can be resolved are about 1 μm in diameter
- Visible light microscopes are adequate for resolving cells (diameters 5-50 μm)
Application of Ultra-Violet (UV) and Infra-Red (IR) Light in Medicine
UV Light
- Photon has energy greater than visible photon
- Wave length: 100-400 nm
- Used in medicine to:
- Kill germs
- Produce more reactions in the skin than visible light
- Cause tanning
- Treat skin cancer
IR Light
- Photon has energy less than visible photon
- Wave length: 700-10000 nm
- Used in medicine to:
- Heat deep tissues
- Provide warmth
- Not usually hazardous even when focused by the cornea and lens of the eye onto the retina
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Description
Explore the properties of light, including its speed, index of refraction, and wave-particle duality, and their significance in medical applications.
