Atomic and Nuclear Physics Answers

A photon and an electron each have an energy of (6.0 X 10^3 eV). What are their

wavelengths? Which of these would you use to probe atomic structures?

238

92U decays spontaneously by α emission to 234

90Th. Calculate the total energy released by

this process and the recoil velocity of the 234

90Th nucleus. The atomic masses are 238.050783

u for 238

92U and 234.043595 u for 234

90Th.

Half life period of U234 is 2.5×105 years. In how many years it will remain 25% of original amount?

In a hydrogen atom, the proton and the electron are separated by an average distance 5 ∙ 10"## �. (a) Calculate the force that the proton exerts on the electron at this distance. (b) Calculate the electric field strength at the average location of the electron.

If a plane cuts the x, y and z axes at -4, 8 and -4 what is the Miller index of the plane?

An even-2, even-N nucleus has the following sequence of levels above its

Ot ground state: 2+ (89 keV), 4+ (288 keV), 6+ (585 keV), 0’ (1050 keV),

2+ (1129 keV). (a) Draw an energy level diagram and show all reasonably

probable y transitions and their dominant multipole assignments. (b) By

considering also internal conversion, what additional transitions and multipoles would appear?

Calculate the work done when an object of mass, 50kg is moved through a distance of 5m. (g=10m/s).

3. The half-life of radium-226 is 1600 years. If a sample of radium-226 has an original activity of 200 Bq, what will it’s activity be after 4800 years?

Sodium-24 has a half-life of 15 hours. If a sample of sodium-24 has an original activity of 500 Bq, what will its activity be after 60 hours?

Carbon-14 is a radioactive isotope of carbon which decays by β− emission. It has a half-life of 5700 years.

a i Explain the meaning of the term half-life.

(1 mark)

ii State the composition of a nucleus.


(2 marks)

b is produced when a nitrogen nucleus first absorbs a neutron in the atmosphere and then the resulting nuclide emits a proton.

i State the nuclear reaction equation for the production of from .


(2 marks)

ii Write down the stable nuclide into whichdecays by β− emission.


(2 marks)

c Living plants absorb carbon dioxide from the atmosphere, a small quantity of which contains. The β− activity, A0, from a living plant remains constant, but once the plant dies the activity decays according to the expression


where A is the activity at time t.

Calculate:

i the decay constant λ for


(2 marks)

ii the ratio .