Measuring Radioactivity - Online Tutor, Practice Problems & Exam Prep

Radiation measurement is crucial in understanding the intensity and impact of radioactive decay. The unit curie (Ci) quantifies radiation as 3.7×10¹⁰ disintegrations per second, while the SI unit becquerel (Bq) represents one disintegration per second. The roentgen (R) measures ionizing intensity of gamma and X-rays without an SI equivalent. The rad, equal to 1×10^-5 joules/gram, and its SI counterpart, the gray (Gy), indicate energy absorbed by tissue. Furthermore, the rem (radiation equivalent man) and sievert (Sv) assess tissue damage, with 1 Sv equating to 100 rem. The relative biological effectiveness (RBE) factor, which is 1 for X-rays, gamma rays, and beta particles, and 20 for alpha particles, accounts for ionizing intensity and biological effect, emphasizing the varying impacts of different types of radiation on biological tissues. Understanding these units and their interrelations is essential for accurately assessing radiation exposure and its potential biological effects.

Units of Radiation Measurement

Here we're going to say that radiation can be measured in several different ways, depending on which property is being measured. So here we're going to have units of radiation measurement. And we need to realize is that there are a lot of common units used for radiation. We have Curie, we have Rd. engine, we have RADS, and we have R.E.M.

All right, so let's start out with our Curies. We're going to say here that one Curie is equal to 3.7×1010 disintegrations per second. And we're going to say that the SI unit is 1 becquerel, which is BQ. So I'm going to butcher some of these because the names are a little bit different than what we're used to seeing. So we're going to say that one BQ is equal to 1 disintegration per second and we're going to say here, what property is it measuring. We're going to say that it's measuring decaying events or decay events.

Next, we have one Rd. engine which is R capital R. We're going to say that one Rd. engine is equal to 2.1×109 charges per centimeters cubed. Here we don't have an SI unit equivalent to it and we need to realize here it deals with the exposure in terms of ionizing intensity of gamma and X-rays.

Next we're going to say we have rads. So we're going to say here, one rad is equal to 1×10-5 Joules over grams, and that one rad is equal to 1 capital R. So it's equal to 1 Rotigen. All right. Next we're going to say the SI unit equivalent of that is Gray or GY. We're going to say here that one Gray is equal to 1 Joule over kilograms, and it's also equal to 1 rad. So you can start seeing that some of these units are connected to one another. This will allow us later on to convert from one radiation unit to another. Now here this deals with energy absorbed by tissue.

Then we have REMS equals RADS times RBE. RBE is your relative biological effectiveness. We're going to say the SI unit of that is our sievert or SV. 1 sievert is equal to 100 R.E.M. And then we're going to say what exactly is the property measuring? It's measuring tissue damage.

Now, finally coming back to RBE, which is your relative biological effectiveness. It factors accounts for both your ionizing intensity and biological effect. And we're going to say here that X-rays, we're going to say here gamma rays, we're going to say here beta particles their RBE is equal to 1 and when it comes to alpha particles which are larger, their RBE is equal to 20.

So here these are the most important types of radiation units that you should keep in mind. Realize only the ones that are in purple remember are purple boxes are the ones that are important in terms of memorization. The others would be given to you in some way, either in a formula sheet or within the question itself.

Measuring Radioactivity Example

The initial responders to Chernobyl nuclear disaster were exposed to 23 SVS of radiation. Convert this value to R.E.M. All right. So all we got to do here is use the conversion factor and realize 23 SV.

The conversion factor is that for everyone SV we have 100 rems. So when we do that, SVS cancel out and we go off with R.E.M. at the end. This comes out to 2300 R.E.M. as the new units for our radiation.

23   SV × 100   rem = 2300   rem

A typical chest X-ray exposes a patient to an effective dose of 0.09 mSv. How many Rad is this?

• A. 25 rad
• B. 0.125 rad
• C. 0.009 rad
• D. 37 rad

Two technicians in a nuclear laboratory were accidentally exposed to radiation. If one was exposed to 5 mGy and the other to 9 rad, which technician received more radiation?

• A. The one exposed to 5 mGy
• B. The one exposed to 9 rad
• C. The two technicians were exposed to the same amount of radiation

A solution of iodine-131, a radioisotope used in the diagnosis and treatment of thyroid disease, is found just prior to administration to have an activity of 1.08 x 10⁶ Bq/mL. If 2.57 mL were delivered intravenously to the patient, what dose of I-131 ( in µCi) did the patient receive?

• A. 7.50×10^–5 µCi
• B. 75.0 µCi
• C. 29.2 µCi
• D. 0.075 µCi
• E. 0.029 µCi

Here’s what students ask on this topic:

What is the unit of measurement for radioactivity?

The unit of measurement for radioactivity is the becquerel (Bq) in the International System of Units (SI). One becquerel is defined as one disintegration or nuclear transformation per second. It indicates the activity of a quantity of radioactive material in which one nucleus decays per second. This unit is named after Henri Becquerel, who shared a Nobel Prize with Pierre and Marie Curie for their work in the discovery of radioactivity.

Another older unit that is still used, particularly in the United States, is the curie (Ci), which is defined as 3.7 × 10¹⁰ disintegrations per second. The curie is a much larger unit than the becquerel and was originally based on the activity of one gram of radium-226. For practical purposes, such as medical treatments and radiation safety, you may encounter submultiples like millicuries (mCi) or microcuries (µCi).

What is the SI unit in the measurement of radioactivity?

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The SI unit used to measure radioactivity is the becquerel (Bq). One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. This unit is named after Henri Becquerel, who was one of the discoverers of radioactivity. It's important to note that the becquerel is a very small unit, so in practical situations, you'll often encounter larger multiples like kilobecquerels (kBq), megabecquerels (MBq), gigabecquerels (GBq), and so on, where each step up represents a thousand-fold increase in activity. Another older unit of radioactivity that is still used in some contexts is the curie (Ci), which is equivalent to 3.7 × 10<sup>10</sup> becquerels.

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What is the unit for becquerel?

The becquerel (symbol: Bq) is the SI (International System of Units) derived unit for radioactivity. One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. It is a measure of the rate at which a given radioactive substance is undergoing radioactive decay. The becquerel is a relatively small unit, and often larger multiples such as kilobecquerels (kBq), megabecquerels (MBq), gigabecquerels (GBq), terabecquerels (TBq), and so on are used when dealing with significant quantities of radioactive substances. The unit is named after Henri Becquerel, one of the discoverers of radioactivity.

What unit is used to measure radioactivity?

Radioactivity is measured in a unit called the becquerel (Bq). One becquerel is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. It's a measure of the rate at which a sample of radioactive material is undergoing nuclear decay. Another older unit of radioactivity is the curie (Ci), which was originally based on the radioactivity of one gram of radium-226. The curie is a much larger unit than the becquerel, with one curie equal to 3.7 × 10¹⁰ becquerels. For measuring radiation dose absorbed by biological tissue, the gray (Gy) is used, and for the risk of radiation exposure, the sievert (Sv) is the unit of choice. Both of these units take into account the biological effects of radiation, not just the activity.