Leaving Cert Physics long questions on Nuclear Physics
2011 - 2002
Solutions begin on page 4
2011 Question 12 (d)
In the manufacture of newsprint paper, heavy rollers are used to adjust the thickness of the
moving paper. The paper passes between a radioisotope and a detector, and a pair of rollers, as
shown.
The radioisotope used is Sr-90 and it emits beta-particles, which are recorded by the detector.
The output from the detector adjusts the gap between the rollers, so that the paper is of uniform
thickness.
(i) Name a suitable detector.
(ii) Describe how the reading on the detector may vary as the paper passes by.
(iii) Why would the radioisotope Am-241, which emits alpha-particles, not be suitable for this
process?
(iv) Calculate the number of atoms present in a sample of Sr-90 when its activity is 4250 Bq.
The half-life of Sr-90 is 28.78 years.
2010 Question 12 (b)
The following reaction occurs in a nuclear reactor:
(i) Identify the element X.
(ii) Calculate the mass difference between the reactants and the products in the reaction
(iii)What is a chain reaction?
(iv) Give one condition necessary for a chain reaction to occur.
(v) Give one environmental impact associated with a nuclear reactor.
2009 Question 12 (d)
Smoke detectors use a very small quantity of the element americium-241. This element does not exist in
nature and was discovered during the Manhattan Project in 1944.
Alpha particles are produced by the americium-241 in a smoke detector.
(i) Give the structure of an alpha particle.
(ii) How are the alpha particles produced?
(iii) Why do these alpha particles not pose a health risk?
(iv) Americium-241 has a decay constant of 5.1 × 10–11 s–1.
Calculate its half life in years.
(v) Explain why americium-241 does not exist naturally.
