Physics Paper 2, MAy/June. 2013
 Questions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Main

Weakness/Remedies
Strength

Question 15

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Observation

Part (a)  This part was answered by many candidates and they fared well in it.
Part (b)  Most candidates seemed not to have an idea of what emission spectra is.  Probably it was not covered by the teacher.  Few candidates could mention the three types of emission spectra but they were unable to mention the which produces each spectrum.
Part (c)  This a numerical part and was fairly tacked by most responding candidates.  However, some candidates mistook the potential difference (V) across the tube for the speed of the electron (v) while substituting into the formula.
Part (d)   Candidates had no problem tackling this part.  Performance was above    average.
15.       (a)   Ionization  Potential (v)

This is the potential absorbed by on atom in its ground state which just removes
an electron completely from the atom
(b)(i)       Types of emission spectra
e.g       -           line spectrum
-           band spectrum
-           Continuous spectrum

NOTE:-  Do not accept absorption spectra.

(ii)    Sources of each emission spectrum
Line spectrum – from atoms in gases e.g
Hydrogen, neon (at low pressure in a discharge tube)

Band spectrum – from molecules
Carbon (iv) oxide (in a discharge tube)
Continuous spectrum – from sun or solids and liquids

(c)(i)     eV  =  ½ mv2
1.6 x 10-19 x 80 x 103= ½ x 9.1 x 10-31 x V2
v2  =  2.81  x 1016
v = 1.68 x 108 ms-1
(ii)    𝛌   =
=  6.6 x 10-34
9.1 x 10-31 x 1.68 x 108

=    4.32 x 10-12 m

(d)        h           =   ½ mv2

1.  x 10-34 x 4.5 x 1018  =  ½ x 9.1 x 10-31 x V2

2.97 x 10-15 = 4.55 x 10-31 x V2
v2  = 6.53 x 1015
v = 8.08 x 107 ms-1