Rehabilitation Physical Agents Quiz

Electromagnetic Spectrum Overview

• All substances emit radiant energy as photons.
• Energy is transmitted through electromagnetic (e.m.) waves with a constant speed of 3 x 10^8 m/sec.
• Waves are defined by their wavelength (distance between corresponding points of consecutive waves) and frequency (number of cycles per unit time).
• The equation V = fλ combines velocity (V), frequency (f), and wavelength (λ).

Wave Properties

• Energy inversely correlates with wavelength; shorter wavelengths correspond to higher energy.
• Higher frequency results in greater energy content.
• Wave frequency influences the depth of penetration into tissues.

EM Spectrum Characteristics

• Ultraviolet (180-400 nm, 1.03 x 10^15 - 7.5 x 10^14 Hz) is used for diagnosis and therapy.
• Cold Laser (632 nm, 4.74 x 10^14 Hz) aids tissue healing.
• Infrared (800-15,000 nm, 2 x 10^14 - 2 x 10^13 Hz) is employed for superficial heat.
• Microwaves (1.5 x 10^4 - 3 x 10^8 Hz) and shortwaves (3 x 10^9 - 30 x 10^7 Hz) provide deep heat diathermy.

Effect of Heat and Chemical Reactions

• Infrared, visible, and ultraviolet rays are thermally produced; infrared heat promotes temperature increase in tissues (Grotthus’ Law).
• Ultraviolet rays induce chemical reactions, such as vitamin D formation.
• Wireless waves generate heat through high-frequency oscillating currents.
• Cold laser light does not generate heat upon absorption.

Wave Behavior Characteristics

• Waves exhibit reflection, refraction, absorption, and penetration.
• Reflection: Rays can be redirected based on wavelength, surface nature, striking angle, and reflector shape.
• Refraction: Occurs when waves bend upon entering a new medium.
• Absorption: Depends on the incident angle, described by the Cosine Law, where maximum absorption occurs at a right angle.

Laws Governing Radiation

• Law of Inverse Squares: Intensity diminishes inversely with the square of the distance from the source (ΔI = 1/(Δd)²).
• Bunsen Roscoe Law of Reciprocity: Intensity and duration of radiant energy doses are inversely related (E = It; E/t = I).
• Cosine Law: Maximum energy absorption occurs when the radiation source is perpendicular to the absorbing surface.
• Grotthus-Draper Law: The biological effect of rays is dependent on the energy absorbed.

This quiz focuses on the electromagnetic spectrum and its relevance to physical therapy (PT). Students are expected to describe the spectrum, outline its sources and characteristics, and explain the pertinent laws governing radiation. Prepare to demonstrate your understanding of how these concepts apply in rehabilitation settings.