Question 1

Which equation correctly describes the number of radioactive nuclei remaining after time $$t if $$the initial number is $$N_0$$ and the decay constant is $$\lambda$$?

Accepted Answer

$$N = N_0$ e$$^{-\lambda t}$$

Question 2

A sample of $$^{14}C in a $$living organism has an activity of $$0.23 Bq $$per gram of carbon. After death, the activity drops to $$0.121 Bq $$per gram. If the half-life of $$^{14}C is$$ $$5730$$ years, what is the approximate age of the sample?

Accepted Answer

$$5300$$ years

Question 3

Which isotope from the table has the longest half-life?

Accepted Answer

$$^{115}_{49}In$$

Question 4

In the radioactive decay series shown, what type of decay occurs when $$^{238}_{92}U$$ transforms into $$^{234}_{90}Th$$?

Accepted Answer

Alpha decay

Question 5

Which of the following is conserved in all nuclear reactions?

Accepted Answer

Total electric charge and total number of nucleons

Question 6

A nuclear reactor uses control rods and a moderator. What is the main function of the moderator?

Accepted Answer

To slow down neutrons so they can cause fission in $$^{235}U$$

Question 7

If the binding energy per nucleon increases after a nuclear reaction, what type of reaction has occurred?

Accepted Answer

Either fusion or fission, depending on the nuclei involved

Question 8

Which nuclear reaction notation correctly represents the reaction: $$\gamma $$+ ^{25}$$_{12}Mg \$$rightarrow ^{24}$$_{11}Na $$+ ^{1}$$_{1}H$$?

Accepted Answer

$$^{25}_{12}Mg (\gamma, p$$) ^{24}$$_{11}Na$$

Question 9

In a chain reaction involving $$^{235}U$$, what condition is necessary for a controlled chain reaction in a nuclear reactor?

Accepted Answer

On average, only one neutron from each fission causes another fission

Question 10

Which equation gives the activity $$A of a $$radioactive sample with $$N$$ nuclei and decay constant $$\lambda$$?

Accepted Answer

$$A = \lambda N$$

Question 11

A nuclear fission reaction of $$^{235}U$$ with a neutron releases approximately how much energy?

Accepted Answer

$$200$$ MeV

Question 12

Why can a thermal neutron penetrate a nucleus more easily than a proton or alpha particle?

Accepted Answer

Neutrons are electrically neutral and do not experience repulsive Coulomb forces

Question 13

Which process is responsible for powering stars like the Sun?

Accepted Answer

Nuclear fusion

Question 14

If a nuclear reaction has a negative Q-value, what does this imply?

Accepted Answer

The reaction is endothermic and requires energy input

Question 15

What is the minimum kinetic energy required for an alpha particle to induce the reaction $$^{4}_{2}He $$+ ^{27}$$_{13}Al \$$rightarrow ^{30}$$_{15}P $$+ ^{1}$$_{0}n if$$ $$Q = -2.64$$ MeV and $$M_{He} = 4.00$$, $$M_{Pn} = 29.98 + 1.01$$?

Accepted Answer

$$3.03$$ MeV

Question 16

Which isotope would be most suitable for dating ancient artifacts, based on its half-life?

Accepted Answer

$$^{14}C$$

Question 17

In the context of nuclear reactors, why is enriched uranium used instead of natural uranium?

Accepted Answer

Enriched uranium contains a higher percentage of $$^{235}U$$, which is more easily fissioned

Question 18

Which of the following best describes the energy conversion process in a nuclear power plant?

Accepted Answer

Nuclear energy is converted to thermal energy, then to mechanical energy, and finally to electrical energy

Question 19

Which nuclear reaction is an example of nuclear fusion?

Accepted Answer

$$^{2}_{1}H $$+ ^{3}$$_{1}H \$$rightarrow ^{4}$$_{2}He $$+ ^{1}$$_{0}n$$

lecture 26

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