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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

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