31.The picture tube of a black and white T.V. set has only one electron gun that produces the picture on its screen. The number of electron guns, a colour picture tube has, is :

32.Soduim thiosulphate is used in photography because :

33.A bubble of water shines because of :

34.One of the youngest sciences of the 20th century which deals with production, control and application of very low temperature is called :

35.The chance of vehicle to overturn whole negotiating a circular path depends on :