Electromagnetic Waves PDF

Electromagnetic Waves Chapter 22 Learning Objectives LECTURE 1 TO EXPLAIN THE ELECTROMAGNETIC SPECTRUM EXLAIN THE PROPERTIES OF THE ELECTROMAGNETIC WAVES EXPLAIN THE MEDICAL USES OF THE ELECTROMAGNETIC WAVES LECTURE 2 EXPLAIN WHAT IS THE MRI AND HOW IT IS WORK...

Electromagnetic Waves Chapter 22 Learning Objectives LECTURE 1 TO EXPLAIN THE ELECTROMAGNETIC SPECTRUM EXLAIN THE PROPERTIES OF THE ELECTROMAGNETIC WAVES EXPLAIN THE MEDICAL USES OF THE ELECTROMAGNETIC WAVES LECTURE 2 EXPLAIN WHAT IS THE MRI AND HOW IT IS WORK EXPLAIN THE SAFTY OF USING MRI EXPLAIN THE PEOPLE WHO ARE NOT ABLE TO USE MRI Introduction Electromagnetic (EM) waves are produced only by charges that accelerate. _ÉI o EM waves, also called electromagnetic radiation, consist of oscillating electric and magnetic fields that travel away from the accelerating charges. Ii 2 A changing magnetic field will induce a changing electric field and vice-versa—the two are linked. These changing fields form electromagnetic waves. minor The electric and magnetic fields sustain each other as the wave travels outward. There are no electric waves or magnetic waves; there are only electromagnetic waves. Electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space. EM waves in vacuum or in air travel at a speed of 3.00 × 108 m/s. i.am mison www.ijjn on a w̅ To msair.im.io am Is The electromagnetic spectrum 5 EM waves can exist at every frequency, without restriction. The properties of EM waves and their interactions with matter depend on the frequency of the wave. The electromagnetic spectrum—the range of frequencies (and wavelengths)—is traditionally divided into six or seven named regions. The electromagnetic spectrum The entire range of wavelengths or frequencies of electromagnetic radiation extending from gamma rays to the longest radio waves is divide into 7 types: i.MIT.FI Gamma rays (< 0.01 nm) X-Rays (0.01 to 10 nm) Ultraviolet(10-400 nm) T.wwiojio.is Visible light(400-700 nm) Infrared (700 nm- 1 mm) samewww.n Microwaves(1 mm to 30 cm) Radio waves (> 30 cm) Iii Visible light Visible light is the part of the spectrum that can be detected by the human eye. is For an average range we take frequencies of 430 THz (1 THz = 10 12 Hz) to 750 THz, corresponding to wavelengths in vacuum of 700–400 nm. I White light can be separated by a prism into the colours red (700–620 nm), orange (620–600 nm), yellow (600–580 nm), green (580–490 nm), blue (490–450 nm), and violet (450–400 nm). to ss o Red has the lowest frequency (longest wavelength), and violet has the highest frequency (shortest wavelength). Lightbulbs, fire, the Sun, and fireflies are some sources of visible light. Most of the things we see are not sources of light; we see them by the light they reflect. Colorimeter and spectrophotometers are working in visible region. www.w.wslw.la  Visible light Medical applications Blue light treatment of jaundice in babies joy  Visible light Scanning laser ophthalmoscope A scanning laser I ophthalmoscope is an instrument that uses a collimated beam of laser light to image the ocular structures of the eye, especially the retina and optic nerve head.  Visible light Photodynamic therapy Is www Photodynamic therapy (PDT) uses a combination of light energy and photosensitizing medications to treat certain types of cancer and other health conditions such as psoriasis, acne and infections. min  Visible light An endoscopy is a test to look inside the body. A long, thin tube with Endoscopy 16W a small camera inside, called an endoscope, is passed into body through a natural opening such as mouth.  Visible light New approaches to Endoscopy  Is To Infrared s larger in wavelength Infrared radiation (IR) is lower in frequency than visible light. a from the low-frequency (red) edge of the IR extends visible to a frequency of about 300 GHz (λ = 1 mm), ie., 700nm – 1 mm. Infrared waves are longer than visible light waves but shorter than radio waves. Infrared light is invisible to the human eye, but some animals can detect IR. The thermal radiation given off by objects near room w̅ temperature is primarily infrared, with the peak of the radiated IR at a wavelength of about 0.01 mm = 10 μm. IR is using in modern thermometers and Thermography.  Infrared Medical application Thermography Thermography is the use of infrared (IR) imaging to assess skin temperature as an extension of the clinician's physical exam to aid in the formation of a medical diagnosis or treatment plan.  Infrared IwzwIwé Pulse oximetry Pulse oximetry uses spectrophotometry to determine the proportion of hemoglobin that is saturated __0 with oxygen  Infrared Near Infrared Spectroscopy Iiii Near infrared spectroscopy (NIRS) is a tool for assessing of the oxygenation status and hemodynamics of various organs, e.g. muscle and brain. o  III Ultraviolet time Ultraviolet (UV) radiation is higher in frequency than visible light. UV ranges in wavelength from the shortest visible wavelength (about 400 nm) down to about 10 nm. 110nm 400mm There is plenty of UV in the Sun’s radiation. UV incident on human skin causes the production of vitamin D. O More UV exposure causes tanning; too much exposure can cause sunburn and skin cancer. UV incident on the eye can cause cataracts. w In medicine, ultraviolet radiation is used to treat certain skin conditions such as psoriasis, vitiligo, and skin tumours of cutaneous T-cell lymphoma. Also called UV radiation. s 28 Microwaves infrared a Microwaves are the part of the EM spectrum lying between radio waves and IR, with vacuum wavelengths roughly from 1 mm to 30 cm. Microwaves are used in communications (cell phones, wireless computer networks, and satellite TV) and in radar. Microwave thermotherapy is being used in medicine for cancer treatment and treatment of other diseases. X-rays and Gamma Rays X-rays have wavelengths ranging from 0.01 to 10 nm, frequency ranging from 30 petahertz to 30 exahertz (3x1016 Hz to 3x1019 Hz). Gamma rays are high energy EM radiation. 51 Pulsars, neutron stars, black holes, and explosions of supernovae are sources of gamma rays that g.gr travel toward Earth, but—fortunately for us—gamma rays are absorbed by the atmosphere. IW Very common application of x-ray in medicine are X-ray imaging and CT scan. at Most diagnostic x-rays used in medicine and dentistry have wavelengths between 10 and 60 pm (1 pm = 10−12 m). In a conventional x-ray, film records the amount of x-ray radiation that passes through the tissue. Computed tomography (CT) allows a cross-sectional image of the body.  X-rays X-ray CT scan X-ray CT scan of chest shows lungs, heart and tumour (red)  X-rays Radiotherapy X-rays or other radiation can damage the DNA in cells and kill them. This is why radiation can be dangerous. But cells which are dividing rapidly are more likely to be killed. So, we use x-rays to kill the rapidly- dividing cancer cells. We must still ensure that healthy tissue is undamaged. A linear accelerator generates x-rays. It rotates around the body, irradiating the tumour from all directions A medical physicist decides which angles to shine x-rays from to destroy tumour and minimise damage to other tissue Radio Waves The lowest frequencies (up to about 1 GHz) and longest wavelengths (down to about 0.3 m) are called radio waves. Radio waves extensively used for communications. The three main Radio wave applications in medicine are: MRI – diagnostic imaging RF ablation – cardiology and cancer (tumour) therapy Localized dielectric heating (shortwave diathermy) – physiotherapy.