Electromagnetic Spectrum Lecture Notes PDF

Electromagnetic Spectrum  Electromagnetic Spectrum Dr/ Hisham Mahmoud Ghorab Lecturer of Physical Therapy Basic Science Department  Objectives - Electromagnetic radiation. - Determine theoretical characteristics of electromagnetic radiation. - Distinguish between ionized...

Electromagnetic Spectrum  Electromagnetic Spectrum Dr/ Hisham Mahmoud Ghorab Lecturer of Physical Therapy Basic Science Department  Objectives - Electromagnetic radiation. - Determine theoretical characteristics of electromagnetic radiation. - Distinguish between ionized and non- ionized radiation. - Explain the laws and interactions governing electromagnetic waves.  Summary - Waves with Low Frequencies have Long Wavelength, Low Energy and High Penetration (Low scattering) - Waves with High Frequencies have Short Wavelength, High Energy and Low Penetration (High scattering)(with concern) -The electromagnetic spectrum is the full range of electromagnetic radiation that travel as waves. -Waves made up of electric and magnetic fields. -Electromagnetic waves are regular sinusoidal. - Electromagnetic waves do not require a medium to travel through. -The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. -The electric and magnetic fields at any point are perpendicular to each other and to the direction of the wave’s motion -Arranged according to frequency, wavelength and energy Passes through space at the speed of light (High Frequency, High Energy as E = h f ). - Wave length (λ): is the horizontal distance between a point on one electromagnetic wave and exactly the same point on the next wave. ( Crest, Trough.. etc) - Wave frequency (f): is the number of cycles that occurs in one second. It is measured in Hertz (Hz) - The relation ship between frequency and wavelength is inversed according to v = λ x ƒ (v is the speed of light, λ is the wavelength, and ƒ is the frequency) - High Frequency (High Energy), Short Wavelength - Low Frequency (Low Energy), Long Wavelength -Lower frequency waves are known as radio waves.(radio and television signals. - Higher frequencies (microwave). Cellular phones, radar, and microwave ovens - Diathermy devices (the shortwave or microwave frequency ranges) - Lasers produce electromagnetic waves from the visible light frequency range. - Much higher frequencies are used to produce x-rays for diagnostic purposes.  Electromagnetic Waves Production - Sufficient intense electrical or chemical forces are applied to any material, this can cause an electron to move out to a higher energy electron orbit level. This said to be the atom in an excited stage. - When the electron returns to its normal level, energy is released due to the difference in levels as a pulse of electromagnetic radiation called a Photon. -The wavelength or frequency of this radiation depends on the energy difference. Non-Ionizing Radiation Low frequency electromagnetic radiation including, shortwaves, microwaves, infrared radiation, visible light, and ultraviolet, is nonionizing and cannot break molecular bonds or produce ions, and can be used for therapeutic medical application. Ionizing Radiation Higher frequency electromagnetic radiation, such as X-ray and Gamma Rays, is ionizing and can break molecular bonds to form ions. Ionizing radiation can also inhibit cell division and is therefore either not used clinically or used in very small doses for imaging or to destroy tissue.  Properties Electromagnetic Waves -They transport electrical and magnetic energy through space at Transverse Direction (not need medium). - All electromagnetic waves have a constant velocity in space 3×10 m/s (Speed of Light). - Different Frequencies in the same field may produce Different Physiological Effects depending on amount of energy they give the tissue. -These waves of energy can be Reflected, Refracted and Absorbed by the media through which they travel. - The Human Body Cannot Detect most electromagnetic waves (Infrared can be detected but X Ray is not) Reflection, Refraction, Absorption and Scattering Reflection Reflection of waves occurs when they pass from one material to another which depends on: a) Nature of the radiation. b) Angle of incidence. c) Nature of the surface. -The angle of incidence is equal to the angle of reflection (which is perpendicular on the surface) - The radiations falling on a surface are either reflected or absorbed. The more reflected, the less absorbed and vice versa -Radiations falling on surface at right angles have the highest level of penetration and least reflection. Refraction - Refraction is the change of direction of radiation when it passes from one medium to another of a different optical density. - Waves is bent or refracted at the boundary with change in velocity, unless it is perpendicular to the surface of the medium. - Angle of refraction depends on: The wavelength of the waves. velocity in the two media. The angle of incidence. Scattering -Scattering is the net result of both reflection and refraction -Electromagnetic radiations passing through non-homogenous tissues change their directions at every tissue interface to different directions, resulting in great reduction in penetration - Longer wave lengths (lower frequency) are scattered less than shorter ones (higher frequency) - ultraviolet radiation is scattered more than infrared radiation and thus has a reduced penetration depth Absorption and Penetration -Absorption and penetration are reciprocal. - Greater absorption means less penetration and vice versa. -For homogenous material, amount of radiation absorbed at any point is fixed resulting in exponential reduction in amount of radiation penetrating with depth of the structure. -Different wavelengths have different penetration depths in particular material -Tissues are not homogenous and thus absorption and penetration in them is irregular.  Laws and Principles Arndt–Schultz Principle Law of Grotthus–Draper Inverse Square Law Lambert Cosine Law Arndt–Schultz Principle -It states that no reactions or changes can occur in the body tissues if the amount of energy absorbed is insufficient to stimulate the absorbing tissues. -The goal of the clinician should be to deliver sufficient energy to stimulate the tissues to perform their normal function. Law of Grotthus–Draper -It describes an inverse relationship between the penetration and absorption of energy. -If the therapeutic energy is not absorbed by the superficial tissues, it will penetrate to deeper tissues. -Higher frequency, shorter wavelength light has a tendency to be absorbed at a more superficial level than has light of longer wavelength. Lambert Cosine Law -The intensity of radiation varies with the cosine of the angle of incidence. Effective energy = energy X cosine of the angle of incidence -Right angles (90°) have the highest level of penetration maximum intensity applied and least reflection. - At incidence angle of 45° the cosine is 0.7 which makes penetration of waves falls to 70% of the maximum. Inverse Square Law -The intensity of radiation from a source is inversely proportional to the square of the distance from that source. -Inverse Square Law; E=Eo/D² E=energy received by the tissues, Eo=energy produced by the source, D2=Distance Squared -The closer the source of radiation, the greater the intensity of radiation being received by the skin, the further away, the less the intensity. Contraindications to Electromagnetic Radiation Problem Cause Pregnancy Energy produced or its physiological effects may affect the fetus. Pacemaker Affects the pacemaker which could be harmful to the patient Recent deep Patients who had it in the past 3 months, might have X-ray therapy reduced sensory sensation and diminish circulation. Metastasis and May accelerate the rate of growth and spread of malignancy malignancy Metal concentrate the energy and cause burn implants Thank you