Card Set Information
lecture 6 and 7 (10-13-11, 10-18-11)
A change in the magnetic field always induces or creates what?
A change in the electric field always induces or creates what?
The changing electric or magnetic fields are repetitive, and do what?
oscillate forming waves
What is an electromagnetic wave?
patterns of magentic and electric fields changing
What speed do electromagnetic waves travel at?
speed of light
Do all waves travel at the same frequency and wavelength?
What changes as waves form a spectrum and the frequencies and wavelengths change?
physical effects change also
What are some examples of the physical effects we manipulate in therapy to treat patients?
What is the electromagnetic spectrum?
graphic representation of the range of wavelength of energy including radiant energy, visible, ultraviolet, and infrared
What is the length of one wave made by one oscillation?
What type of electromagnetic waves have the longest wavelength? (lower frequency)
What waves have shorter wavelengths? (higher frequency)
infrared, visible, ultraviolet
What has the shortest wavelength and highest frequency of all?
What are wavelengths measured in?
What is frequency?
number of oscillations per second
What is frequency measured in?
What are hertz?
cycles per second
If a wavelength is longer, what is the frequency?
If the wavelength is shorter, what is the frequency?
What type of wavelength gives the deepest penetration?
What type of frequency gives the deepest penetration?
What type of frequency gives superficial penetration?
In the electromagnetic spectrum, what waves have the highest frequency?
2. gamma rays
*these are like treble, higher and not as deep
What is in the middle of the spectrum?
violet - higher frequency
red - lower frequency
What waves on the spectrum have lower frequencies?
3. shortwaves / radiowaves
*like bass, deeper and lower
1 Hz equals what?
1 cycle per second
Different wavelengths and frequencies form different what?
What is a medium?
environment energy is going through
Radiant energy can be effected by a medium in what 4 ways?
1. absorbed (what we want)
2. reflected (bounce off body, dont affect tissues)
3. refracted (ends up at different angle)
4. passes right through (has no affect at all)
What law states that electromagnetic waves must be absorbed in order to produce effects?
grotthus draper law
What is the cosine law?
maximum absorption is going to occur at a right angle to the surface of the skin
What is the inverse square law?
the intensity of the energy is inversely proportional to the distance of the source
*if distance is greater the intensity is less,
*if the distance is smaller, the intensity is greater
What law states waves change direction sometimes while passing through certain mediums (snells law)?
law of refraction
What law states energy that is absorbed is used, but not all the energy is absorbed?
law of absorption