Observation

Part (a): Performance was poor. Many candidates failed to correctly define those concepts signifying complete ignorance.
Part (b): Performance was good as many candidates were able to respond correctly to this questions.
Part (c): Majority of the candidates correctly differentiated between soft x-rays and hard x-rays and also gave correct reason for doping a semiconductor material but many could not give the correct circuit symbol for a p-n junction diode.


The expected answer is
(a) (i) Definition of atomic spectra
The emission of light from a substance when its excited electrons move to lower energy level.
OR
Distinct/separate bright lines of light of definite frequency/wavelength (emitted from vapourized atoms).
(ii) Differentiating between emission spectra and absorption spectra
Emission spectra is the pattern of light displayed when electrons jump from a higher energy level to a lower energy level, while absorption spectra is the displayed pattern of wavelengths absorbed by the gas.



(c) (i) Differentiating between soft x-rays and hard x-rays
Soft x-rays are those with longer wavelengths/lower penetrating power/ less energy while hard x-rays are those with shorter wavelengths/higher penetrating power/more energy.
(ii) Circuit symbol of p-n junction diode
(iii) Reason for doping a semiconductor material
To increase the electrical conductivity/reduce electrical resistivity of the semiconductor.