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RadTech: Physics - Ch.5


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What is an 'energy continuum'?
The wide range of energies existing in an uninterrupted ordered sequence.
What is a photon?

What is another name for it?
The smallest quantity of any type of electromagnetic radiation.

A Quantum.
What is the speed of light?
3 x 10⁸ m/s
What are Sine waves
Variations of amplitude over a period of time to a discrete mathematical formula.
What is the symbol for frequency?

How is it defined?
f or Hz (cycles per second)

The rate of rise and fall of a sine wave.

Frequency is equal to the number of times the like parts of a sine wave pass an observed point per unit of time.
What is the symbol for wavelength?

How is it defined?

The distance between two like points on the sinewave.
What is the Wave Equation?

How is it written for the speed of light?
V = fλ

C = fλ
What is the electromagnetic spectrum?
The entire range of electromagnetic radiation.
What are the regions of the EM spectrum that are important to radiologic technology?
1. Radiofrequency 10⁶ to 10⁸ Hz
MR Imaging.

2. Visible Light ∽ 10⁻⁶to10⁻⁷ m

3. X-radiation 10⁴ to 10⁵.⁵keV
How are energy and frequency of a photon related?
They are directly proportional.
Define Refraction.
The deeviation in the course of visible light when it passes from one transparent medium to another.
What is infrared light light?
Photons whose wavelength is longer than visible light but shorter than microwaves.
What is ultraviolet light?
Photons whose wavelength is shorter than visible light but longer than ionizing radiation.
What is the character of RF energy and wave lengths?
Very low energy and very long wave length.
Wha is used to characterize ionizing radiation?
The energy contained in a photon, in keV.
What is the source of X-rays?
They are emitted from the electron cloud of an atom that has been artificially stimulated.
What is the source of Gamma rays?
They are emitted from the nucleus of a radioactive atom that is undergoing decay.
What is Wave-Particle Duality?

What is generally true of photon behavior regarding this?
Photons exhibit both Wave and Particle types of behavior.

Photons interact with matter most easily when the matter is approximately the same size as the photon wavelength.
With regard to Wave-Particle Duality, how do X-rays behave?
Like particles.
How does EM radiation with wavelength longer than X-rays behave?
Like waves.
With regard to visible light, what determines which wavelengths are reflected?
The atomic and molecular structures of the objects they hit.
What is radiation attenuation?
The reduction in intensity resulting from scattering and absorption in the material they are passing through.
Define radiopaque and radiolucent.
Radiopaque - the capacity to absorb X-rays.

Radiolucent - the capacity to attenuate X-rays.
What is the Inverse Square Law?
Intensity is inversley proportional to the square of the distance from the source.

I1/I2 = (D2/D1)squared
What is the qualifying factor for distance when using the Inverse square Law?
The distance must be seven times greater than the longest dimension of the source.
What is the X-ray energy range?
10keV to 50Mev.
What is the velocity of X-rays?
The speed of light.
What is the relationship of the E and M fields in a photon?
They both vary sinusoidally with the same frquency and wavelength and are at 90 deg. to each other.

Their amplitudes peak in the middle and diminish at each end.
What is the relationship between photon energy and frequency?
They are directly proportional.
What is Planck's Constant?

What is its formula?
The constant of proportionality between photon energy and frequency.

E = Hf

H = 4.15 x 10⁻₁⁵ eV
= 6.63 x 10⁻₃⁴ J
What is the Law of Conservation of Energy?
Energy can neither be created nor destroyed, but can be transformed.

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