radium
thorium
lead
polonium
Radioactive elements can be traced out in living cell through a technique called
Radioactive elements emit:
Railway tracks are banked on curves
Railway tracks are banked on curves so that
Rain drops acquire spherical shape due to
Rain is falling vertically downwards. To a man running east-wards, the rain will appear to be coming from
Rainbow is due to
Rainbow is formed due to
Rainbow is seen after rain as of hanging molecules of water which act as
Rainbows are produced when sunlight: