UNIT I NON IONIZING
RADIATION AND ITS MEDICAL APPLICATION (Regulation 2013)
Non-ionizing
Electromagnetic Radiation: Overview of non-ionizing radiation effects-Low
Frequency Effects- Higher frequency effects. Physics of light, Measurement of
light and its unit- limits of vision and color vision an overview,
Thermography– Application
Light - Physics of light, Intensity of light, limits of Vision and color vision Sound -Physics of sound , Normal sound levels – Ultrasound fundamentals- Generation of ultrasound ( Ultrasound Transducer) – Interaction of Ultrasound with Materials-Reflection and Refraction – Absorption and Scattering Non- ionizing Electromagnetic Radiation. Tissue as a leaky dielectric – Relaxation Processes – Overview of non – ionizing - radiation effects -Low Frequency Effect – Higher frequency effect.
Light is a form of energy. Light is a transverse, electromagnetic wave visible to human eye and is responsible for the sense of sight. Like all electromagnetic waves, light can travel through a vacuum. It has dual nature. (Particle and wave).The wave nature of light was first illustrated through experiments on diffraction and interference. The transverse nature of light can be demonstrated through polarization. The particle nature of light can be through photo electric effect and Compton Effect. Visible light has wavelength in a range from about 380 nano meter to about 740 nm, with a frequency range of about 405 THz to 790 THz.
Intensity is a measure of the power emitted by a light source in a particular direction per unit solid angle. The SI unit of luminous intensity is the candela (cd).
limits of Vision
Short sight (myopia)
Short sight (myopia)
Short sight is where the eyeball is elongated or the lens is too thick, causing the image to focus in front of the retina. Short sight means that the image is focused in front of the retina.
Long sight (hypermetropia)
Long sight is where the eyeball is too short or the lens too thin, causing the image to focus behind the retina. Long sight means that the image is focused behind the retina.
Both caused by the cornea and lens not focusing properly on the retina and both can be overcome by wearing glasses.
There are other sight-threatening conditions which are not so easily corrected or overcome. Cataract, trachoma, glaucoma and river blindness will cause complete blindness if left untreated.
