Chemistry
Sodium vapour lamps glow with yellow colour. This is due to

The low ionisation energy of sodium
Its ability to absorb all other colours except yellow
The emission of excess energy absorbed by sodium atoms, in the yellow region of the spectrum
sublimation of sodium to emit yellow colour

ANSWER DOWNLOAD EXAMIANS APP

Chemistry
Water cycle refers to

Constant movement of water from ocean to land and back to ocean once again
Scientific management of water in areas excessively plagued with water-logging
An integrated attempt to recycle water in relatively arid regions
Water distribution in relatively dry areas

ANSWER DOWNLOAD EXAMIANS APP