Electromagnetic Spectrum Overview

Electromagnetic Spectrum

• Electromagnetic (EM) waves are created by vibrations between electric and magnetic fields.
• EM waves are composed of oscillating magnetic and electric fields.
• EM waves are formed when an electric field interacts with a magnetic field.

Learning Objectives

• Students will be able to categorize different constituents of the electromagnetic spectrum in order of increasing or decreasing wavelength/frequency.
• Students will be able to list applications of each constituent of the electromagnetic spectrum.

Electromagnetic Waves

• Electromagnetic waves travel in a straight line until they encounter a different medium.
• They can be transmitted, reflected, or absorbed.
• Reflection involves an incident angle equal to the reflected angle.
• Reflection principles guide the design of reflectors for redirecting rays to a target. In IR and UV lamps, parabolic reflectors are commonly used because they reduce the concentration issues from other reflector shapes.
• Reflection can be used in infra-red and ultraviolet therapy to properly direct rays to the appropriate target.
• reflection is a crucial concept in ultrasound therapy, helping to properly treat tissues or to move through different tissues or mediums

Electromagnetic Spectrum Detail

• The electromagnetic spectrum encompasses a range of waves with varying wavelengths and frequencies.
• Gamma rays, X-rays, ultraviolet (UV) light, visible light, infrared (IR) light, microwaves, and radio waves are all part of this spectrum.
• Wavelengths are measured in nanometers (nm)
• Frequencies are measured in Hertz (Hz)
• Shorter wavelengths correspond to higher frequencies and higher energy.
• Longer wavelengths correspond to lower frequencies and lower energy.

Infra-Red Radiation

• Infra-red (IR) radiation is part of the electromagnetic spectrum.
• The range of IR radiation is from approximately 1mm to 700-750nm

Refraction

• Refraction occurs when EM rays pass from one medium to another with differing optical densities.
• The ray bends based on the media and the angle of incidence.
• Snell's Law describes refraction.
• Refraction has applications such as coupling media (e.g., water) in ultrasound treatments.

Absorption

• Grotthus law explains that EM rays might be absorbed in a new medium, resulting in an effect.
• Absorption degree is reliant on wavelength, medium properties, and the angle of incident.
• Absorption is impacted by the wavelength, the properties of the medium, and the incident angle.

Law of Grotthus-Draper

• The law of Grotthus-Draper describes the inverse relationship between penetration and absorption of energy.
• If the tissues aren't absorbing energy, then that energy can penetrate deeper into the body.

Inverse Square Law

• The intensity of radiation is inversely proportional to the square of the distance from the source.
• The closer a source of radiation is to someone, the greater the intensity of the radiation.
• The further away the source of radiation is, the less intense the radiation.

Cosine Law (Right Angle Law)

• Optimal radiation occurs when the radiation source is perpendicular to the target area.
• A non-perpendicular angle can lead to less radiation being directed into a targeted area.

Ultraviolet Rays

• Ultraviolet (UV) rays have higher frequencies and shorter wavelengths than visible light.
• UV rays have higher energy than visible light.
• UV rays contribute to Vitamin D production in the skin.
• These rays are used in eye surgery and sterilizing surgical instruments.
• Excessive UV exposure can cause damage.
• UV rays penetrate tissues, promoting therapeutic effects.

Non-Ionizing Radiation

• Non-ionizing radiation encompasses various EM radiations with frequencies below 10^15 Hz and wavelengths between 10^-8 and 10^4 meters.
• Non-ionizing radiation does not break molecular bonds.
• It is used in therapeutic medical practices.

Ionizing Radiation

• Ionizing radiation has enough energy to break molecular bonds, creating ions.
• Examples include X-rays and Gamma rays.
• Ionizing radiation can be used for medical imaging (in small doses) or to destroy tissue (in larger doses).

Short Wave Diathermy

• Short-wave diathermy is a method using high-frequency EM waves.
• Short-wave diathermy is used to heat deep tissue sections of the body.
• Short-wave diathermy has a frequency of 27.12 MHz, a wavelength of roughly 11 meters.

Microwave Diathermy

• Microwave diathermy is a type of electromagnetic treatment with wavelengths between 0.1 and 100 cm.
• It employs magnetrons to generate microwaves.
• Microwave diathermy focuses better and is more efficient.

Radiotherapy

• Radiotherapy is a cancer treatment that uses high-radiation doses to kill cancerous cells.
• Radiotherapy uses small doses of radiation for diagnostic purposes such as X-rays and examining broken bones.

Gamma Rays

• Gamma rays have short wavelengths and high frequencies, higher than X-rays.
• They carry the most energy and penetrate deeply.
• Gamma rays are used for radiation cancer treatment.

Practice MCQs

• Questions and answers assess students' understanding of the concepts.

This quiz covers the fundamentals of the electromagnetic spectrum, focusing on the properties and behaviors of electromagnetic waves. Students will explore the categorization of different constituents based on wavelength and frequency, as well as their applications in real-world scenarios.