(a)(i) What is meant by the term artificial radioactivity? (ii) Complete the table below Emission...
(a)(i) What is meant by the term artificial radioactivity?
(ii) Complete the table below
| Emission | Nature | Charge | Ionizing |
| High speed electron | Moderately ionizing | ||
| Neutral | Negligible ionizing ability | ||
| Alpha particles | Positive |
(b) In an x-ray tube, an electron is accelerated from rest towards a metal target by a 30 kV source. Calculate the kinetic energy of the electron. [e=1.6 x 10\(^{-19}\)C]
(c) The table below shows the frequencies of radiations incident on a certain metal and the corresponding kinetic energies of the photoelectrons.
| Frequency x 10\(^{14}\)(Hz) | 6.8 | 8.0 | 9.2 | 10.0 | 11.0 |
| Kinetic energy x 10\(^{-19}\)(j) | 0.8 | 1.6 | 2.4 | 2.9 | 3.8 |
(i) Plot a graph of kinetic energy, K.E, on the vertical axis and frequency, f, on the horizontal axis starting both axes from the origin (0,0).
(ii) From the graph, determine the:
i. Planck's constant;
ii. Threshold frequency of radiations;
iii. Work function of the metal.
Explanation
(a)() Meaning of artificial radioactivity;
The process by which a stable nucleus is bombarded with a neutron to make it unstable and so disintegrates/decays with the emission of particles/radiation and. energy.
| Emission | Nature | Charge | Ionizing |
| Beta (\(\beta\)) | High speed electron | Negative | Moderately ionizing |
| Gamma (\(\gamma\)) | Electro-magnetic radiation | Neutral | Negligible ionizing ability |
| Alpha particles | Helium nucleus | Positive | Highly ionizing |
(b) Calculation of kinetic energy
K.E = eV
= 1.6 x 10\(^{-19}\) x 30 x 10\(^{3}\)
= 4.8 × 10\(^{-15}\)J
(c)(i) graph of K.E versus f
i. Both axes correctly distinguished
ii. Reasonable scale on both axes
(ii) (I) Planck's constant. h = slope of the graph Slope
i. \(\bigtriangleup\)K.E and \(\bigtriangleup\)f correctly determined
ii. \(\frac{\bigtriangleup K.E}{\bigtriangleup f}\) corectly determined and recorded within range.
(II) Threshold frequency, f\(_{0}\) .
The intercept on the horizontal or frequency axis.
(III) Threshold frequency, W\(_{o}\)
Negative intercept on K.E axis.