physics midterm

Target interactions at the anode produce:

99% thermal energy & 1% Brehms & Characteristic photons

T/F An increase in current equals an increase in the number of electrons boiling off the filament (thermionic emission) which equals an increase in the number of x-rays.

\n

t

Decreasing kVp 

Increases patient dose

What is the point source of x-ray photons

The target area

All is true about the Focusing Cup except 

\
Low negative potential applied

Compresses the thermionic cloud

Usually composed of Nickel

High positive potential applied

High positive potential applied

Generally, what charge does the **focusing cup** have in an x-ray tube designed for general x-rays?

negative

What is considered the x-ray quantity 

mA  number of electrons crossing the tube

What describes the distance an x-ray beam travels in matter?

penetrability

What is outside the tube

stator

The faster the anode rotates, the better the heat ______________. \n The use of stationary anode x-ray tubes has become limited \n to low-power functions, such as those of dental units.

dissapation

changes in kVp create changes in beam penetrability, kVp is the primary controller of the differences in densities - These is know as

contrast

exposure time is __________ proportional to the number of electrons crossing the tube and is, therefore, directly proportional to the number of x-rays created.

directly

How do radiations differ along the electromagnetic spectrum?

Radiations along the electromagnetic spectrum will vary according to their associated \n frequencies and wavelengths. Low frequencies and long wavelengths are at the bottom end of the \n spectrum with radio waves and microwaves. Visible light is in the center of the spectrum, and at \n the top of the spectrum are gamma and x-rays with associated high frequencies and short \n wavelengths

Photon energy and frequency are \n directly proportional. T/F

T

Ohm’s law

Ohm’s law describes the relationship between current and potential difference as \n follows: the current along a conductor is proportional to the potential difference. \n V= IR, I = V/R, and R = V/I are also correct

What is rectification

rectification is the process by which alternating current is changed to pulsating direct current

What does The electrical production of x-rays need?

These include a source of electrons, an appropriate target material, a high voltage, and a \n vacuum

cathode assembly includes-

filament or filaments, focusing cup, and associated \n wiring

purpose of focusing cup

The purpose of the focusing cup is to narrow the thermionic cloud as it is driven toward \n the anode. Because electrons all possess negative charges, their tendency is to diverge \n rather than travel in straight lines. The focusing cup is provided with a low negative \n current that, because of its geometry, focuses the electrons toward one another in a \n convergence pattern

WHAT IS TUNGSTEN

is the metal of choice for the source of x-ray photons because it has a high \n atomic number, a high melting point, and good heat-conducting ability

anode heel effect

fat cat

what increases the dissipation of heat?

high-speed rotating ANODES

vacuum function

permits electrons to flow from cathode to anode without encountering the \n gas atoms of air. This greatly increases the efficiency of the tube’s operation

What produce s the x-ray photons and consists of less than 1 percent of \n the total kinetic energy of the incident electrons

target interactions

99% of…

heat

1% of..

x rays

How many electrons can the "L" shell hold?

8

Which of the following has the longest wavelength?

radio waves

One of the laws of electrostatics is like charges  ________ ; unlike charges _________ .

repel, attract

Ohm's Law can be written as:

amps = volts/ohms

An electrical circuit with each component having individual branches is called

paralllel circuit

Total resistance for a parallel circuit is:

The sum of the reciprocal of each resistance

Electrification by induction is the process of electrical fields acting upon one another:

without contact with each other

The fundamental component of the atom with the greatest mass is:

neutron

Electron binding energy depends on:

how close it is to the nucleus,how many protons there are in the nucleus

What is the K-shell binding energy of Tungsten?

69\.5 keV

The wavelength and energy of an x-ray photon produced when an incident electron is weakly redirected by the nucleus of the Tungsten atom will be:

long and low

The anode is the ----- end of the x-ray tube

positive

Bremsstrahlung x-rays are created:

when an incident electron approaches near the nucleus of a Tungsten atom

is there electron activity in anode?

no

What is an anode assembly that turns during exposure

rotating anodes

The most common diagnostic radiography target angle is

12

An emission spectrum of diagnostic x-rays is made up primarily of:

bremmstahlung x ray photons

increasing kVp will have what effect on x-ray photon production on the emission spectrum?

increase

What brings the filament up to current needed

rotor

The atomic mass number =

protons and neutrons

How many heating charts are available to help radiographers avoid thermal damage to x-ray tubes

3

what does the protective housing of the x-ray tube do: choose all that apply

Controls leakage radiation

cools the tube

creates a charge that heats up the fan

insolates high voltage away from the radiographer

Controls leakage radiation

cools the tube

insolates high voltage away from the radiographer

is the unit used to describe the product of tube current and exposure time.

mA

as the mA doubles, so does the number of_______ able to cross the tube. 

electrons

The focal spot is also know as 

Target Area, Focal Point, Focal Tract,

The inverse square law states

as SID increases, image receptor exposure decreases. As SID decreases, image receptor exposure increases

As x-ray _______ energy increases, the penetrating ability of the photon increases. 

photon

What is true about the 15 % rule?

increase in kVp of only 15% will demonstrate a doubling in image receptor exposure

X-ray exposure time is measured in 

secinds

1 meter is equal to 

100 cm

Which of the following is affected by the milli-amperage per second?

image receptor exposure

What is the relationship of mAs and Image Receptor Exposure

density is primarily determined by the amount of exposure a film receives, and because exposure is directly proportional to mAs, mAs is used as the primary controller of radiographic film density and image receptor exposure. 

low kVp produces high or low contrast?

high contrast(mostly black and white)

high kvp produces high or low contrast?

low contrast (many shades of gray)

relationship w contrast and oid

direct

elationship w contrast and mA

none

relationship w contrast and kVp

indirect

relationship w contrast and filtration

indirect

relationship w contrast and amount of tissue

indirect

relationship w contrast and grid ratio

direct