Physics Paper 2, MAy/June. 2010

Questions:	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	Main

General Comments
Weakness/Remedies
Strength

Question 15 (a) State three conclusions that can be drawn from Rutherford's experiment on the scattering of alpha particles by a thin metal foil in relation to the structure of the atom. The diagram above illustrates the energy levels of an electron in an atom. If an excited electron moves from n2 to ns. Calculate the: (i) frequency; (ii) wavelength of the emitted radiation. [h = 6.6 X 10-34 Js; 1eV= 1.6 X 10-19 J; C = 3.0 X 108 ms" ] (c)The following nuclear equations represent two types of radioactivity. Identify each type and explain briefly the difference between them.

Observation
Part (a). Performance was fair Part (b) Candidates registered commendable success. Part (c) Most of the respondent candidates successfully identified the given equations, A and B. However, some confused the equation with fusion and fission reactions. The expected answers are: (a) Any three correct conclusions E.g. The nucleus is massive Most of the atom is empty space The nucleus is positively charged Electrons revolve round the nucleus It explains the periodicity of elements in the periodic table (b )(i) E₂₀ = E₂- E₀ = -2.0 - (-12.0) = 10.0 e V = 10 x 1.6 x 1O-19J = 1.6x10-18J E=hf Or f =E/h = 1.6 x 1018 6.6 x10-34 = 2.424 x 1015 Hz (ii) c = fλ λ= c/f = 3 X 10⁸ 2.424 x 10¹⁵ (c) A: Natural radioactivity B: Artificial radioactivity Any correct difference