Physics 3LC Week 7

Which of the following safety rules should you follow when working with radioactive substances? A. Return all sources to the closed, labeled container handled by your T.A. B. When counting samples, do not stand beside the source. C. Mouth pipetting, eating, drinking, and smoking are prohibited. D. Wash your hands following the laboratory E. All of the above.

At a distance of 9 cm from a presumably isotropic, radioactive source, a pair of students measure 65 cps (cps = counts per second). On average, how many counts per second do you expect at a distance of 29 cm? (Note that the average number of counts per second need not be an integer.)

In Part 7.2.2 of the experiment, a pair of students measure the signal from a cobalt source for 10 sec and find C = 25 counts. They decide to repeat the measurement, but this time read only C = 20 counts. What is wrong? A. They did not count for long enough time intervals B. Nothing is wrong; cobalt has a really short half-life C. Nothing is wrong; there is a certain amount of statistical uncertainty in the measurement D. The Geiger counter is probably broken

For an unknown sample of the experiment, students measure 1660 counts when they first receive their sample and 1309 counts 5 minutes later. Calculate the half-life of their sample. min ?

Given Graph Semilog paper is a convenient tool for analyzing data that changes exponentially. The scale on the y axis of the paper is logarithmic. Since the logarithm of an exponential function is a linear function, exponentially varying data appear as a straight line on semilog paper. Suppose that in Part 7.2.3 of the experiment, students created the above graph based on their data. What is the half-life in minutes?

Which of the following is NOT an example of a type of molecular change within the cell typically leading to cellular damage? A. A hydrogen radical and a hydroxyl radical combining to form a water molecule. B. Ionization of a water molecule into a hydrogen radical and a hydroxyl radical. C. A single strand break in double stranded DNA. D. All of the above are examples of molecular change leading to cellular damage

Which of the following cellular properties would make the cell more susceptible to damage by ionizing particles? A. High rate of mitosis B. Cellular division throughout a major portion of the organisms lifetime C. Lack of specialization in a cellular developmental sequence D. All of the above would make the cell more susceptible to damage

Why are the similarities of cesium to potassium and strontium to calcium important? A. Cesium and strontium are easily converted into potassium and calcium, respectively, INCREASING their half-life. B. They are readily assimilated into the body, INCREASING the amount of radiation damage. C. They are readily assimilated into the body, DECREASING the amount of radiation damage. D. Cesium and strontium are easily converted into potassium and calcium, respectively, DECREASING their half-life.

What factors affect the biological half-life? A. Size of particle B. Mode of intake C. Water solubility of material D. All of the above affect the biological half-life

As an example, mercury-203 is a radioisotope that is important for kidney function studies and renal imaging. The physical half-life, , is 46.6 days and biological half-life, , of is 10.3 days. What is the effective half life of mercury-203? days