Agl helps in artificial rain because:

The clouds consist of charged particles of water dispersed in air. Some of them are +vely charged, other are -vely charged. When +vely charged clouds come closer they cause lightening and thundering whereas when +ve and -ve charged colloid come closer they cause heavy rain by aggregation of minute particles. It is possible to cause artificial rain by throwing electrified sand or silver iodic from an aeroplane and thus coagulating the mist hanging in air. Smoke screen is a cloud of smoke used to hide military, naval police etc. It consists of fine particles of TiO_(2) . AgI helps in artificial rain because :

Silver iodide is used for producing artificial rains because Agl

Viruses cannot multiply of their own or be grown in vitro on artificial medium because they

Explain the following : (a) Same substance can act both as colloids and crystalloids. (b) Artificial rain is caused by spraying salt over clouds.