Chapter 7 Test: Radioactivity
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- 1.
Background measurements and counting rates from a paper filter attached to a vacuum cleaner for one hour were taken at three locations. The results are shown on the table below. The background was not subtracted. All rates are in counts per minute. Location X Location Y Location Z Background Filter 18 19 16 85 31 29
- 2.
The table below summarizes the results of an experiment in which a Geiger counter operated with no substances held near it, then with equal masses of compounds of elements W, X, Y, and Z held near it at equal distances. Compound Elements in Compound Counts during a one-minute interval Trial I Trial II Trial III None 1 2 3 4 None WX WY ZX ZY 6 91 97 8 9 13 100 90 9 7 5 94 99 8 6
- 3.
- 4.
PLEASE TYPE YOUR ANSWERS TO THE FOLLOWING QUESTIONS IN THE SPACE PROVIDED, YOU MAY USE A SEPARATE SHEET TO WORK OUT THE ANSWER.
- 5.
Explain your answer to number 13. Use complete sentences.
- 6.
In class we measured the radiation given off by a small sample of radioactive barium. We noted that the number of counts decreased over time (i.e., it showed a “half-life”). Why does the radiation decrease as a radioactive sample ages? In other words, what is happening to the radioactive material that causes it to give off less radiation as time passes? USE COMPLETE SENTENCES.
- 7.
The table below shows the net counting rate for radioactive material collected on filter paper. Time (min.) Net counting rate (counts/min) 0 20 40 60 80 100 120 440 340 230 170 95 60 45 On graph paper, plot the data on a graph that shows the net counting rate as a function of time. Draw a smooth curve that represents the general trend of the data (a “curve of best fit”). Note: This graph is worth 3 points
- 8.
What would the 'net counting rate' be after 160 minutes, and why?
- 9.
Six background readings were taken with a Geiger counter over one-minute intervals. The numbers of counts recorded per minute were: 22, 18, 22, 26, 22, and 28. What do you think would have been the result of the next measurement, in counts/min?
- 10.
From your curve, determine the approximate half-life of this material.
- 11.
Which of the following materials are able to block some form of radiation?
- A.
Lead foil
- B.
Skin
- C.
Clothing
- D.
All of the above
- E.
None of the above
Correct Answer
D. All of the aboveExplanation
All of the materials mentioned in the options are able to block some form of radiation. Lead foil is commonly used as a radiation shield due to its high density and ability to absorb radiation. Skin acts as a natural barrier and provides some protection against radiation. Clothing, especially thick and tightly woven fabrics, can also block certain forms of radiation from reaching the body. Therefore, all of the above options are correct as they can block some form of radiation.Rate this question:
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- 12.
Samples of three substances (I, II, and III) were left several days on a piece of photographic film wrapped in light-tight paper, as shown in figure (a). The appearance of the film after being developed is shown in figure (b). Based on this which of these substances seems to be the most radioactive?
- A.
I, II, and III
- B.
I and III only
- C.
I only
- D.
II only
- E.
III only
Correct Answer
C. I only -
- 13.
A sample of radioactive material is held a certain distance away from a Geiger counter. Which of the following procedures would not affect the counting rate?
- A.
Placing a 6-foot-thick iron and concrete wall between the sample and the counter.
- B.
Lowering the temperature of the sample
- C.
Reducing the mass of the sample
- D.
Waiting a billion years and coming back to test it again
Correct Answer
B. Lowering the temperature of the sampleExplanation
Lowering the temperature of the sample would not affect the counting rate because temperature does not have a direct impact on the radioactive decay process. Radioactive decay is a random process that is not influenced by external factors such as temperature. Therefore, changing the temperature of the sample would not alter the rate at which the radioactive material emits particles that can be detected by the Geiger counter.Rate this question:
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- 14.
A background measurement lasting one hour gave 15 counts/min. Shortly after the measurement was completed, another background measurement lasting just one minute found 10 counts. How would you explain the difference between the two results?
- A.
Something must have blocked the radiation from reaching the counter in the second measurement.
- B.
Fewer counts are expected in 60 seconds than an hour.
- C.
The difference of 5 counts/min was due to the presence of radon.
- D.
Radioactivity is not perfectly predictable. Therefore the number of counts measured in a short time span may or may not match up with the long-term average.
Correct Answer
D. Radioactivity is not perfectly predictable. Therefore the number of counts measured in a short time span may or may not match up with the long-term average.Explanation
The difference between the two results can be explained by the fact that radioactivity is not perfectly predictable. Therefore, the number of counts measured in a short time span may or may not match up with the long-term average. In this case, something may have blocked the radiation from reaching the counter in the second measurement, resulting in fewer counts being recorded in just one minute compared to the average counts recorded in one hour.Rate this question:
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- 15.
When a radioactive substance is placed in a cloud chamber, we can actually see the evidence that . . .
- A.
One substance is changing into another substance.
- B.
Radioactivity was discovered by humanity in the late-1800s.
- C.
The substance is not pure; it is a mixture.
- D.
Radioactive decay releases tiny particles--individual atoms.
- E.
Dry ice is really frozen carbon dioxide.
Correct Answer
D. Radioactive decay releases tiny particles--individual atoms.Explanation
When a radioactive substance is placed in a cloud chamber, we can actually see the evidence that radioactive decay releases tiny particles--individual atoms. This is because the cloud chamber allows us to visualize the paths of these particles as they ionize the vapor in the chamber, creating visible trails. This observation provides direct evidence that radioactive substances undergo decay, where unstable atomic nuclei break down and emit particles in the process.Rate this question:
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- 16.
At which location or locations was radioactive material floating in the air?
- A.
Location X
- B.
Location Y
- C.
Location Z
- D.
Location Y and Z
- E.
Location X and Z
Correct Answer
B. Location YExplanation
The correct answer is Location Y because it is the only location mentioned that has radioactive material floating in the air. The other locations, X and Z, do not specify the presence of radioactive material in the air.Rate this question:
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- 17.
What conclusion can be reached based on the data from location Z?
- A.
The filter has a negative net count which means the air removed radiation from it.
- B.
The filter has a net count of 29, and thus is radioactive.
- C.
The filter has a net count of basically zero which means there was no radioactive material floating in the air.
- D.
The Geiger counter needs a new battery.
Correct Answer
C. The filter has a net count of basically zero which means there was no radioactive material floating in the air.Explanation
Based on the data from location Z, the conclusion that can be reached is that there was no radioactive material floating in the air. This is indicated by the fact that the filter has a net count of basically zero, meaning that it did not remove any radiation from the air.Rate this question:
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- 18.
From the results of this experiment, which element would probably be gone if we came back and tested again in 500 million years?
- A.
W, X, and Y only
- B.
W only
- C.
X only
- D.
Y only
- E.
All of the elements W, X, Y, and Z
Correct Answer
B. W onlyExplanation
Based on the given information, the element that would probably be gone if we came back and tested again in 500 million years is W only. This is because the other elements X and Y are not mentioned to be gone, and the element Z is not mentioned at all. Therefore, the most likely answer is that only element W would be gone in 500 million years.Rate this question:
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- 19.
Suppose a chunk of compound XY equal to the mass of the samples used above was held at the same distance from the counter. The counter is run for one minute. What range of counts per minute would you expect to see?
- A.
5 to 13
- B.
10 to 26
- C.
91 to 100
- D.
182 to 200
- E.
No counts
Correct Answer
A. 5 to 13Explanation
If a chunk of compound XY with the same mass as the samples used above is held at the same distance from the counter and the counter is run for one minute, it would be expected to see a range of counts per minute between 5 and 13.Rate this question:
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- 20.
The type of radiation most able to pass through objects is:
- A.
Alpha radiation
- B.
Beta radiation
- C.
Gamma radiation
- D.
Delta radiation
Correct Answer
C. Gamma radiationExplanation
Gamma radiation is the correct answer because it consists of high-energy photons that can easily penetrate through most materials. Unlike alpha and beta radiation, which are made up of particles that can be stopped by a sheet of paper or a few centimeters of air, gamma radiation has no mass or charge, allowing it to pass through objects more easily. Delta radiation is not a recognized type of radiation, making it an incorrect answer.Rate this question:
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- 21.
During a background measurement, a Geiger counter counted 1440 counts in 60 minutes. What was the background radiation?
Correct Answer
24 counts/min, 24 counts/minute, 24 counts per minute, 24 counts per min, 24 counts / minute, 24 counts / minExplanation
The Geiger counter counted 1440 counts in 60 minutes. To find the background radiation, we divide the total counts by the time in minutes: 1440 counts / 60 minutes = 24 counts per minute. Therefore, the background radiation is 24 counts per minute.Rate this question:
- 22.
The table below summarizes the results of an experiment in radioactivity. Compound Elements in compound Radioactivity as determined by a Geiger counter 1 Actinium, bromine Radioactive 2 Potassium, bromine Radioactive 3 Barium, bromine Non-radioactive 4 Uranium, chlorine Radioactive From the results of this experiment alone, which elements are definitely NOT radioactive?
Correct Answer
barium and bromine, barium, bromine, barium bromine, bromine, barium, barium and bromine, barium bromineExplanation
Based on the results of the experiment, we can determine that compound 3, which contains barium and bromine, is non-radioactive. Therefore, we can conclude that barium and bromine are definitely not radioactive.Rate this question:
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