Discrete Energy & Radioactivity (DP IB Physics: HL)

 decays to thorium-234 by emitting an alpha particle and two gamma rays. Thorium-234 then decays into protactinium via beta decay.

Which point on the N-Z graph below represents the position of the granddaughter nucleus, protactinium?

The half-life of carbon-14 is 6000 years.

An ancient elephant tusk has been uncovered and its age is unknown. A 20 g sample of the tusk has an activity of 1.25 Bq due to carbon-14.

A 80 g sample of tusk taken from a living elephant has an activity of 20 Bq.

Use this information to determine the age of the ancient tusk.

Fluorodeoxyglucose is a compound used as a tracer in medical imaging. The isotope fluorine-18 is used, which is a positron emitter.

The way these positrons interact with electrons in the body allows PET (positron emission tomography) scanners to determine the rate of respiration certain cells are performing.

Fluorine-18 decays into an isotope of oxygen.

Which equation below represents the correct nuclear equation for this decay?

Protactinium-231 () is a radioactive element, it decays by alpha radiation and then beta-minus decay as shown below:

 

What proton number and mass number will element B have?

	Proton Number	Mass Number
A.	89	229
B.	90	229
C.	89	227
D.	90	227

The energy levels of an atom are shown in the diagram below.

Which transition will emit the photon with the shortest wavelength?

A radioactive source is known to emit  radiation. A Geiger-Muller tube is used to measure the count rate at increasing distances from the source.

Wh_ich graph correctly represents the variation in count rate over these distances for  radiation?

Unstable nuclei make up 10% of a sample’s mass. The count rate of the sample is measured over a time period of 8 hours.

After some time has passed, the percentage of the sample which is unstable reduces to 2.5%. What is the count rate of the source at this time?

A source is known to be radioactive but the type of radiation being emitted is unknown.

A Geiger-Müller tube is placed close to the source and different materials are placed between the two. A table of the count rates recorded for each material is shown below. The background count rate is 15 counts per minute.

Material	Count rate recorded / counts per minute
Paper	528
Nothing	1064
Thick lead	17
Aluminium	524

What types of radiation are being emitted by the source?

Hydrogen atoms feature energy levels as shown below.

Which photon energy will not cause an electron to be excited or ionised in a ground state hydrogen atom?

Three of the four isotopes below are the same element. Which isotope represents a different element?

	Nucleon number	Neutron number
A.	233	141
B.	235	143
C.	238	146
D.	239	146

The energy level diagram below shows six possible transitions between the energy levels of an atom. Each transition between levels creates a photon of definite energy and frequency.

The increase in frequency is from left to right.

Which of the following spectrum corresponds most closely to the transitions?

A particular nucleus, decays to form , which then has two possible decay paths, resulting in either an isotope of Thallium (Tl) or Polonium (Po), as shown.

Which isotope could not be ?

The decay series for Thorium–232 can be plotted as shown.

According to the diagram, how many possible routes are available for Thorium–232 to decay to a stable nucleus of lead−208?

The diagram shows the decay chain for a particular isotope.

What are the isotopes labelled 1, 2 and 3?

	1	2	3
A
B
C
D

Polythene film is made by extruding polythene and drawing it into a long sheet which is wound onto a roll, as shown in the diagram below.

The manufacturer has to carefully choose a radioactive isotope which will effectively remove any electrostatic charge that has built up on the film. The manufacturer also has to consider the point X, Y or Z at which the radioactive isotope should be placed along the assembly line.

At which point should the radioactive isotope be placed, and which type of radiation should the manufacturer choose to remove excess electrostatic charge?

	Point	Type of radiation
A	X	alpha
B	X	gamma
C	Y	beta
D	Z	alpha

Transitions between three energy levels in a particular atom give rise to the three spectral lines of frequencies, in decreasing magnitude , and with wavelengths , and .

Which of the following correctly relates , and  and ,  and . 

	Frequency	Wavelength
A.
B.
C.
D.

Radioactive isotopes are used in medical imaging.

For example, two isotopes of iodine, 123-I and 131-I are both used by radiographers, who give them to patients in the form of iodide before taking scans.

The possible decay equations for these isotopes are:

1. + _____

      2. + _____

Which is a correct difference between these two decays?

The graph shows the how the neutron-proton ratio of stable nuclei changes as proton number increases.

What other changes with increasing proton number are suggested by the graph?

1. The charge-mass ratio increases
2. The charge-mass ratio decreases
3. The likelihood of α-decay increases
4. The likelihood of β-positive decay increases
5. Protons outnumber neutrons in large nuclei, with a rapidly increasing ratio

The charge to mass ratio, , is also known as the specific charge.

What is the ratio of ?

The number of undecayed atoms, N, of a radioactive substance after time, t, can be calculated by the equation:

Where:

• = the half-life 
• = the original number of atoms

Two radioactive elements X and Y have half–lives T_X and T_Y respectively. An initial sample contains three times as many atoms of X, N_X than atoms of Y, N_Y.

After a certain time, t, which of the expressions for is correct?