WAEC Physics 2012 Theory — Question 8

Model answer

(a) Lighting in a fluorescent tube operates on the principle that an electric discharge through mercury vapour in the tube produces ultraviolet radiation, which then strikes the phosphor coating on the inside of the tube, causing it to fluoresce (emit visible light). (b) Factors determining the colour of light produced: (i) The type/composition of the phosphor coating used inside the tube. (ii) The pressure/composition of the gas (mercury vapour and inert gas) inside the tube.