Most candidates were not able to give an acceptable definition of diffusion though they were able to state the applications of electrical conduction through gases.  Many defined diffusion as movement of particles from region of high concentration to a region of low concentration.  Many candidates still  confuse diffusion with Osmosis.

 

The expected answers are:

(a)        Diffusion is the process by which substances mix (intimately) with one another                              due to the random motion of their molecules.                                        
                        OR
[Scattering of a beam of light on reflection from a rough surface / transmission through certain materials]

(b)        Any two correct applications  
e.g       in
-           advertising industry / Neon signs
-           lighting / fluorescent tubes
-           identification of gases
-           cathode ray oscilloscope / T.V. tube