ASNT RT II Flashcards
Low voltage x-ray tubes are generally fitted with windows made of?
Berylium
Monochromatic x-ray beam is?
a beam consisting of a single wavelength
The general method of producing x-rays involves the sudden deceleration of high velosity electrons in a solid body called a?
target
If it were necessary to radiogragh a 7 in. thick steel product. which of the following gamma ray sources would most likely be used?
Co-60
A Co-60 gamma ray source has an approximate practical thickness limit of?
9 inches of steel or its equivalent
The absorption of gamma rays from a given source when passing through matter depends on the?
atomic number,density,and thickness of the matter
The fact that gasses, when bombarded by radiation,ionize and become electrical conductors make them useful in?
radiation detection equipment
The velocity of electrons striking the target in an x-ray tube is a function of the?
voltage difference between the cathode an anode
The uneven distribution of developed grains within the emulsion of a processed x-ray film causes the subjective impression of?
graininess
Co-60 is reported to have a half-life of 5.3 years.By how much should exposure time be increased when the source is two years old?
31% longer
A source of ir-192 provides an optimum exposure of a given test object today in a period of 20 minutes.what exposure time is needed 5 months from now?
1 hour and 20 minutes
- The gamma ray intensity at 30 cm (1ft) from a 37 GBq (1 Ci) source of radioactive Co-60 is nearest to:
15 roentgens per hour
The focal spot in a X-ray tube:
should be as small as possible without unduly shortening the life of the tube
In an X-ray tube, the filament and focusing cup are the two essential parts of the:
cathode
The quantiy or radiation which will produce, by mean of ionization, on electrostatic unit of electricity in 0.001293 g of dry air is known as
roentgen
The specific activity of an isotopic source is usually measured in:
curies per gram (Ci/g)
Which of the following isotopes has the longest half-life?
cs-137
The primary form of energy conversion when electrons strike a target in an X-ray tube results in the production of:
heat
The slope of a straight line joining two points of specified densities on a characterisitc curve of a film is known as the:
average gradient
An X-ray film having wide latitude also has by definition:
low contrast
The purpose for circulatng oil in some types of X-ray tubes is to:
dissipate heat
An X-ray tube with a small focal spot is considered better than one with a large focal spot when it is desired to obtain:
better definition
one method of reducing radiographic contrast is to:
decrease the wavelength of the radiation used
Thin sheets of lead foil in intimate contact with X-ray film during exposure increase film density because they:
emit electrons when exposed to X and gamma radiation which helps darken the film