Radioactivity

A scientist performs an experiment with a sealed source that emits $\beta$-particles. The distance travelled by the $\beta$-particles in air is about $30\,\text{cm}$. Which precaution would best protect the scientist from the radiation?

Feb/March 2016

Which row provides the description of $\alpha$-particles and of $\gamma$-rays?

Feb/March 2016

A nucleus of the radioactive nuclide $^{218}_{84}\text{Po}$ first undergoes $\alpha$-decay and then $\beta$-decay. After both decays have occurred, what are the nucleon (mass) number and proton (atomic) number of the nuclide produced?

Feb/March 2016

A scientist performs an experiment with a sealed source that emits $\beta$-particles. The distance travelled by the $\beta$-particles in air is around $30\,\text{cm}$. Which precaution would be the most effective for protecting the scientist from the radiation?

Feb/March 2016

Which row gives the properties of $\alpha$-particles and of $\gamma$-rays?

Feb/March 2016

The three ionising radiation types are alpha, beta and gamma.

Feb/March 2016

An isotope of iodine, $^{131}_{53}\text{I}$, undergoes $\beta$-emission to form an isotope of xenon (Xe).

Feb/March 2016

A radioactive substance gives off radiation at a rate of 600 emissions per second. After four hours, its radiation emission rate has fallen to 300 emissions per second. What is the half-life of the substance and what is the rate of emission after another four hours?

Feb/March 2017

A radioactive source is positioned close to a detector. The radiation reaching the detector from the source is recorded for 10 minutes while different materials are placed between the source and the detector. Which kinds of radiation does the source emit?

Feb/March 2017

A radioactive material gives out radiation at a rate of $600$ emissions per second. After four hours, its radiation rate is $300$ emissions per second. Determine the substance’s half-life, and state the emission rate after another four hours.

Feb/March 2017

The equation shows an isotope of radium Ra decaying into an isotope of radon Rn, together with the emission of particle X. $^ {226}_{88}\text{Ra} \rightarrow ^ {222}_{86}\text{Rn} + X$. What is particle $X$?

Feb/March 2017

An atomic nucleus undergoes one or more radioactive decay processes. Which decay process makes the proton number fall by $1$?

Feb/March 2017

Nuclear power stations generate a useful type of energy. Fig. 4.1 shows a section of a nuclear reactor.

Feb/March 2017

A radioactive source is positioned 20 mm from a radiation detector, as shown in Fig. 11.1. The detector first records a count rate of 150 counts/s. A sheet of paper is inserted between the source and the detector. The detector count rate then drops to 60 counts/s. Keeping the paper in position, a magnetic field is applied at right angles to the direction of the radiation. The detector count rate then drops to 20 counts/s. The count rates have not been background-corrected. The background count is 20 counts/s.

Feb/March 2017

Which energy source is used in a nuclear power station to produce electrical energy?

Feb/March 2018

While measuring emissions from a radioactive rock that has been brought into the laboratory, a teacher says that background radiation has to be included. What is meant by this background radiation?

Feb/March 2018

The graph indicates how the percentage of a radioactive isotope remaining changes with time. A student finds the initial emission rate of this isotope to be 40 emissions per second. How long does it take for the emission rate to drop to 5000 emissions per second?

Feb/March 2018

The radioactive isotope of hydrogen decays by beta emission into the isotope $^{3}_{2}\text{He}$. What is the nuclide notation of the hydrogen isotope?

Feb/March 2018

While measuring the emissions from a radioactive rock that has been brought into the laboratory, a teacher says that background radiation has to be considered. What does background radiation mean?

Feb/March 2018

When solid caesium-137 decays by emitting a $\beta$-particle, solid barium-137 is produced, and this then emits a $\gamma$-ray. The barium-137 does not undergo any further decay. Caesium-137 has a half-life of 33 years. A pure block of caesium-137 has a mass of $2.0\,\mu\text{g}$. The diagram shows a radiation detector placed $5\,\text{cm}$ from the block. The detector gives a count rate of 2000 counts/second. Which statement is incorrect?

Feb/March 2018

Fig. 12.1 illustrates a radioactive source positioned near a radiation detector and counter. The detector is able to detect $\alpha$, $\beta$ and $\gamma$ radiation. The radioactive source emits only $\beta$-particles.

Feb/March 2018

ought to be stored.

Feb/March 2018

A student measures the level of radiation given off by a radioactive sample. The table lists the counter readings she records during a short interval of time: $106$, $96$, $98$, $100$ counts per minute. After the sample is taken away, the counter then gives a background radiation reading of $4$ counts per minute. What is the best estimate of the average count rate from the radioactive sample?

Feb/March 2019

Four students are talking about ideas on radioactive decay. Which student’s statement is correct?

Feb/March 2019

A radioactive isotope of carbon $^{14}\text{C}$ undergoes beta decay to produce an isotope of nitrogen $^{14}\text{N}$ together with a beta particle. The reaction is represented by the equation below. $^{14}_{X}\text{C} \rightarrow {}^{14}_{7}\text{N} + {}^{0}_{Y}\beta$ What are the values of $X$ and $Y$?

Feb/March 2019

A beta particle is an electron moving at high speed. Which statement explains how beta particles are released from an atom?

Feb/March 2019

Astatine-210 is a radioactive substance. Its nucleus may be written using the symbol $^{210}_{85}\text{At}$.

Feb/March 2019

Complete the nuclide equation for this decay process: $^{194}_{77}\text{Ir} \rightarrow \;\ldots\ldots\text{Pt} + \ldots\ldots\beta$.

Feb/March 2019

A student determines the rate at which ionising radiation is emitted by a radioactive substance. He positions a detector at several different distances from the radioactive source. The table shows how the counter reading changes with distance $d$. The counter readings have been corrected to allow for background radiation. Which type of ionising radiation is being emitted by the substance?

Feb/March 2020

The graph plots the count rate from a radioactive source as time passes. What is the half-life of the source?

Feb/March 2020

The diagram illustrates the path taken by $\alpha$-particles as they move between two charged plates. Their path bends downwards. What occurs to $\beta$-particles passing through the same electric field?

Feb/March 2020

The graph displays how the count rate from a radioactive source varies with time. What is the half-life of the source?

Feb/March 2020

The nuclide notation for a nucleus of americium-241 is $^{241}_{95}\text{Am}$.

Feb/March 2020

Hydrogen-1 is the isotope with proton number 1 and nucleon number 1. The helium isotopes are helium-3 and helium-4. For helium-3, the proton number is 2 and the nucleon number is 3. For helium-4, the nucleon number is 4.

Feb/March 2020

The diagram illustrates a radioactivity experiment. If a sheet of paper is placed in as the absorber, the count rate falls to the background count rate. Which radiation is being emitted by the source?

Feb/March 2021

The graph illustrates how the count rate from a radioactive sample varies over time. What is the half-life of this sample?

Feb/March 2021

A laboratory technician measures the count rate from a radioactive source and enters the readings in a table. The average background radiation in the laboratory is $8$ counts per second. What is the source's half-life?

Feb/March 2021

Carbon-12 is a stable isotope belonging to carbon. Its nuclide notation is shown in Fig. 11.1. Carbon-14 is an unstable isotope belonging to carbon. Its nuclide notation is shown in Fig. 11.2. Fig. 11.1 shows $^{12}_{6}\text{C}$. Fig. 11.2 shows $^{14}_{6}\text{C}$.

Feb/March 2021

State the proton number, nucleon number and charge of an $\alpha$-particle.

Feb/March 2021

What does the term artificial source of background radiation mean?

Feb/March 2023

A sample of a radioactive isotope begins with an emission rate of 128 counts per minute and has a half-life of 4 days. After how many days will the emission rate decrease to 32 counts per minute?

Feb/March 2023

A radioactive isotope sample has an initial emission rate of 128 counts per minute and a half-life of 4 days. How much time will pass before the emission rate decreases to 32 counts per minute?

Feb/March 2023

Several scientists are working in a laboratory. They are carrying out experiments using sources that emit ionising radiation. Each scientist is issued with a set of safety rules. Three of these rules are shown. Which safety rules protect against the effects of ionising radiation?

Feb/March 2023

The energy produced by stable stars comes from nuclear reactions. What type of reaction takes place in the Sun?

Feb/March 2023

Americium-241 is a radioactive nuclide, and a nucleus of americium-241 is written in nuclide notation as $^{241}_{95}\text{Am}$.

Feb/March 2023

Explain what nuclear fission means.

Feb/March 2023

Which apparatus is used for measuring background radiation?

Feb/March 2024

Which row correctly states the type of each radioactive emission?

Feb/March 2024

A nucleus emits radiation on its own and changes into the nucleus of another element. What could the radiation emitted be?

Feb/March 2024

The diagram shows a lead-lined box that is used to keep a radioactive source. Why is the box lined on the inside with lead?

Feb/March 2024

A student is investigating the count rate of a radioactive substance. How should he adjust his reading to allow for the background count?

Feb/March 2024

The radioactive isotope radon, $^{222}_{86}\text{Rn}$, undergoes alpha $(\alpha)$ emission. As this decay occurs, an isotope of polonium, Po, is formed. How many neutrons are present in the nucleus of this polonium isotope?

Feb/March 2024

Which statement lists two safety precautions that should be followed when someone is working with ionising radiation?

Feb/March 2024

Complete the particle labels for Fig. 10.1. Write the name of each particle on the dotted line.

Feb/March 2024

Most of the alpha particles pass straight through the thin foil. State what this observation tells you about atoms.

Feb/March 2024

In a laboratory, a radiation detector is linked to a counter that gives a reading for the count rate caused by background radiation. In what unit is count rate measured?

Feb/March 2025

Which statement correctly describes alpha, beta and gamma emissions?

Feb/March 2025

What is one effect that ionising nuclear radiation has on living things?

Feb/March 2025

A uranium nucleus $^{{238}}_{{92}}\text{U}$ undergoes decay to produce thorium by releasing an $\alpha$-particle. Thorium then decays into protactinium by releasing a $\beta$-particle. Which row shows the atomic number and mass number for this isotope of protactinium?

Feb/March 2025

Which row indicates what occurs when a nucleus decays by releasing a $\beta$-particle?

Feb/March 2025

Which precaution does not necessarily lower a scientist’s exposure when handling sources of ionising radiation?

Feb/March 2025

A detector is positioned close to a radioactive isotope and registers a count rate of $700\ \text{counts/min}$. The isotope has a half-life of $8\ \text{min}$. The mean background count rate is $60\ \text{counts/min}$. What count rate does the detector record after $16\ \text{min}$?

Feb/March 2025

A nucleus of the nitrogen isotope, N, captures a neutron. It then changes into a carbon isotope, C, and gives out $x$. $^{{1}}_{{0}}\text{n} + ^{{14}}_{{7}}\text{N} \rightarrow ^{{14}}_{{6}}\text{C} + x$. What is $x$?

Feb/March 2025

Table 11.1 provides details about the particles found in an atom.

Feb/March 2025

Strontium-90 ($^{90}_{38}\text{Sr}$) refers to a radioactive isotope of strontium.

Feb/March 2025

A radioactive nucleus gives out either an $\alpha$-particle or a $\beta$-particle. What products result from these two kinds of radioactive emission?

May/June 2016

A measurement is recorded every 10 minutes for the number of emissions per second from a radioactive source. The table lists the measurements. Time / min: 0, 10, 20, 30, 40, 50, 60 Number of emissions per second: 800, 560, 400, 280, 200, 140, 100 What is the half-life of the source?

May/June 2016

Which row gives the nature and one property of all $\beta$-particles?

May/June 2016

The graph illustrates how the decay rate of a radioactive source varies over time. What is the activity at $8$ days?

May/June 2016

Radioactive materials must be handled with care. Which safety precaution does not lower the risk for people using a radioactive material?

May/June 2016

A specimen of a radioactive isotope begins with an emission rate of 128 counts per minute and has a half-life of 4 days. How much time will pass before the emission rate decreases to 32 counts per minute?

May/June 2016

The setup illustrated is used to determine whether the flour in a cardboard packet is above a particular level. If the flour is higher than this level, it absorbs the radiation from the source, preventing it from reaching the detector. Which type of radiation is suitable for use?

May/June 2016

A nucleus of americium $^{243}_{95}\text{Am}$ releases an $\alpha$-particle, producing a nucleus of neptunium (Np). Which equation describes this decay?

May/June 2016

A measurement is recorded every 10 minutes for the number of emissions per second from a radioactive source. The table gives the measurements. What is the half-life of the source?

May/June 2016

Energy can be released during some nuclear reactions. Which nuclear reaction occurs in a nuclear power station, and which nuclear reaction occurs in the Sun?

May/June 2016

A radioactive decay process can be shown as follows. $^{{233}}_{{91}}\text{Pa} \rightarrow ^{{233}}_{{92}}\text{U}$ This equation is not complete. During this decay, the nucleus is altered by

May/June 2016

The graph illustrates how the decay rate of a radioactive source varies over time. What is the decay rate at $8$ days?

May/June 2016

Sodium-24 undergoes decay to magnesium-24 as represented by the equation: $^{24}_{11}\text{Na} \rightarrow ^{24}_{12}\text{Mg} + \text{emitted particle}$. Which particle is emitted?

May/June 2016

A detector positioned close to a radioactive material shows a count rate of 536 counts per second. The background count rate is 44 counts per second. The half-life of the radioactive material is 34 hours. What will the detector reading be after 68 hours?

May/June 2016

A teacher uses two radioactive sources. One source emits only alpha particles, whereas the other emits only beta particles.

May/June 2016

State what a β-particle is and state its charge.

May/June 2016

State what a β-particle is, and indicate its charge.

May/June 2016

Bismuth-214 is radioactive, and its half-life is 20 minutes.

May/June 2016

Radon-220 is a radioactive isotope. The nuclide notation for radon-220 is $^{220}_{86}\text{Rn}$. Describe the make-up of a neutral atom of radon-220.

May/June 2016

The sample is made up of atoms from one specific protactinium isotope, $^{X}_{Y}\text{Pa}$.

May/June 2016

A sample containing a radioactive isotope is decaying. Which atoms’ nuclei will decay first?

May/June 2017

A radioactive isotope has a half-life of $4.0\,\text{years}$. One sample of this substance contains $24$ million radioactive nuclei. After $12$ years, how many of the radioactive nuclei will still be undecayed?

May/June 2017

A sample that contains a radioactive isotope is decaying. Which atoms have nuclei that will decay first?

May/June 2017

The diagram illustrates a decay curve for a radioactive substance. From the curve shown, what is the background radiation count?

May/June 2017

At which type of power station are atoms from one element converted into atoms of different, lighter elements?

May/June 2017

A nuclide of element X undergoes $\beta$-decay. Which statement is correct?

May/June 2017

A sample containing a radioactive isotope is undergoing decay. Which atoms’ nuclei decay first?

May/June 2017

A detector of ionising radiation records a background count rate of $20$ counts/minute. A radioactive isotope whose half-life is $2.0$ days is placed near the detector. The detector reading rises to $100$ counts/minute. How long is it before the detector reading falls to $40$ counts/minute?

May/June 2017

A sample of radioactive isotope is decaying. Which atoms’ nuclei will decay first?

May/June 2017

A sample of a radioactive isotope gives off particles at a rate of 240 per minute. After 48 hours, the emission rate falls to 15 per minute. What is the half-life of the radioactive material?

May/June 2017

A sample containing a radioactive isotope is undergoing decay. Which atoms’ nuclei will decay first?

May/June 2017

A student measures the half-life of a radioactive isotope. Over a five-minute interval, the student uses a detector and draws a graph to show how the count rate on the detector changes with time. The count rate from background radiation is $30$ counts per minute. What is the half-life of this isotope?

May/June 2017

Iodine-131 is a radioactive isotope of iodine. It decays by emitting a $\beta$-particle and a $\gamma$-ray.

May/June 2017

Fig. 12.1 shows the particles in an atom of lithium. A neutron and another particle X are labelled, and electrons are shown on orbits. Fig. 12.1 is not to scale.

May/June 2017

A scientist has obtained a radioactive-substance sample.

May/June 2017