(iii) How much energy is produced when a deuterium nucleus ( 1 2 H), combines
with a tritium nucleus ( 1 3 H)?
(v) Fusion can only take place at very high temperatures. Explain why. 2010
9. When electrons hit the target in an X-ray tube, only a small percentage of their energy is converted into X-rays. What happens to the rest of their energy and how does this influence the type of target used?
(9)
A potential difference (voltage) of 40 kV is applied across an X-ray tube. Calculate: (i) the maximum energy of an electron as it hits the target (ii) the frequency of the most energetic X-ray produced.
(Plank’s constant = 6.6 × 10–34 J s; charge on electron = 1.6 × 10–19 C) 12. (b) The following reaction occurs in a nuclear reactor:
235U + 0 1 n → 141Ba+ X + 3 0 1 n + 202.5 MeV
(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? Give one condition necessary for a chain reaction to occur.
(iv) Give one environmental impact associated with a nuclear reactor. (speed of light = 3.0 × 108 m s−1; 1eV = 1.6 × 10–19 J)
2007 12. (d) Explain the term half-life.
(6) (9)
(9) (4)
(18)
(iv) Calculate the force of repulsion between a deuterium and a tritium nucleus when they are 2 nm apart in free space.
(9) (5)
(11)
(6)
A sample of carbon is mainly carbon-12 which is not radioactive, and a small proportion of carbon-14 which is radioactive. When a tree is cut down the carbon-14 present in the wood at that time decays by beta emission.
Write a nuclear equation to represent the decay of carbon-14.
An ancient wooden cup from an archaeological site has an activity of 2.1 Bq. The corresponding activity for newly cut wood is 8.4 Bq. If the half-life of carbon-14 is 5730 years, estimate the age of the cup.
Name an instrument used to measure the activity of a sample. What is the principle of operation of this instrument?
