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Ch 3-4 Bushong

S1 Unit2 SJ Hooi Equipment

What's this?Oh yeah, that
Ever present all around us is a field or state of energy called ______ electromagnetic energy
Photon The smallest quantity of any type of electromagnetic radiation; it may be pictured as a small bundle of energy, sometimes called a quantum.
Radiolucency Characteristic of materials that allow x-rays to penetrate with a minimum of attenuation. Radiolucent structures are nearly invisible on radiographs.
The inverse square law A mathematical relationship describing the reduction in radiation intensity with distance from a point source. The intensity is inversely proportional to the square of the distance of the object to the source. (Formula)
Frequency The number of wavelengths passing a point per second.
The law of conservation of energy Energy can be transformed into another form or into matter, but it cannot be created or destroyed.
Gamma ray A form of ionizing electromagnetic radiation emitted from the nucleus of a radioactive atom.
Electromagnetic spectrum The wide range of electromagnetic radiation described by its frequency, wavelength, or energy.
Sinusoidal (sine) variation The mathematical or graphical description of a simple harmonic motion.
Quantum A single unit of electromagnetic radiation.
Visible light A narrow region in the middle of the electromagnetic spectrum extending from approximately 400 nm (blue) to 700 nm (red).
A thunderclap associated with lightning has a frequency of 800 Hz. If its wavelength is 50 cm, what is its velocity? How far away is the thunder if the time interval between seeing the lightning and hearing the thunder is 6s? Velocity = 400 m/s. Distance = 2400 m or approximately 1½ miles.
What is the frequency associated with a photon of microwave radiation that has a wavelength of 10−4 m? Velocity = frequency × wavelength 3 × 10^12 Hz
Radio station WIMP-FM broadcasts at 104 MHz. What is the wavelength of this radiation? Velocity = frequency × wavelength 2.88 m
What is the wave equation? Velocity = frequency × wavelength (v = f × *) *symbol for wavelength
How are frequency and wavelength related? Inversely. As frequency increases, wavelength decreases proportionately.
The intensity of light from a reading lamp is 200 millilumens (mlm) at a distance of 2 meters (m). What is the intensity of light at 3 m? 89 mlm.
What are the three imaging windows of the electromagnetic spectrum, and what unit of measure is applied to each? Radiofrequency by frequency (Hertz), visible light by wavelength (meters), and x-radiation by energy (electron volts).
What is the energy range of diagnostic x-rays? (20-)30 – 150 keV.
What is the difference between x-rays and gamma rays? Origin. X-rays are emitted from the electron cloud. Gamma rays are emitted from the nucleus.
Some regions of the electromagnetic spectrum behave like waves, and some regions behave like particles in their interaction with matter. What is this phenomenon called? Wave-particle duality
Define attenuation (from book) The reduction of x-ray beam intensity because of absorption and scatter.
Electric charge and its unit 1 Coulomb = 6.3 × 10^18 electrons.
Electrodynamics Electric charges in motion.
Electric power P+IV Electric power (P/W) = Electric current (I/A) × Electric potential (V).
Electrostatics Stationary electric charges.
Dipole A dipole is an object with two poles.
Induction The ability to transfer energy from one object to another without touching.
Magnetic domain An accumulation of many atomic magnets with their dipoles aligned.
Autotransformer An iron core transformer with only one winding.
Gauss; Tesla Both are units of magnetic intensity. 10,000 gauss = 1 tesla.
Electric potential The energy per unit charge that causes electrons to move in an electric conductor; electric potential is measured in volts (V).
List the four laws of electrostatics Unlike charges attract; like charges repel; Coulomb’s Law of electrostatic force; electrostatic force follows the inverse square law; electric charges are uniformly distributed except at regions of high curvature where they are concentrated.
A radiographic exposure requires 100 mAs. How many electrons is this? 100 mAs = 0.1 C = 6.3 × 1017 electrons.
Describe three types of transformer Closed-core transformer, autotransformer, and shell-type transformer.
What are the three ways to electrify an object? Contact, friction, induction.
A mobile x-ray imaging system operates on 110 V AC power. Its maximum capacity is 110 kVp and 100 mA. What is the turns ratio of the high- voltage transformer? 1000:1
Magnetic fields in excess of 5 G can interfere with cardiac pacemakers. How many mT is this? (5 G/10000) = 0.5 mT
What is the role of magnetism in the study of x-ray imaging? The high-voltage generators in x-ray imaging systems are magnetic devices. Magnetic resonance imaging deals with static and varying magnetic fields.
List the three principal types of magnets. Permanent magnets; electromagnets; superconducting magnets.
Describe an electromagnet. Current-carrying coil wrapped around a ferromagnetic core.
Explain how a magnetic domain can cause an object to behave like a magnet The magnetic domain causes the internal dipoles of the object to align, thus the object turns into a magnet.
State Ohm’s how and describe its effect on electric circuits. Voltage is equal to the product of current and resistance. It is a characteristic used in the design of all electric circuits.
What happens when a bar magnet is heated to a very high temperature? It loses its magnetic properties.
List three diamagnetic materials Wood, water and plastics.
Where in everyday life might one find an electromagnet? Automatic door opening devices and other controllers.
What is the range in intensity of the Earth’s magnetic field? From approximately 50 to 100 T.
Created by: paigeduh