Questions

Sea appears blue in colour due to the scattering of the rays when they hit water molecules

RADAR - RAdio Detection And Ranging.

A radar system consists of a transmitter producing electromagnetic waves in the radio or microwaves domain, a transmitting antenna, a receiving antenna (often the same antenna is used for transmitting and receiving) and a receiver and processor to determine properties of the objects. 

Radar is an object-detection system that uses radio waves to determine the range, angle, or velocity of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain.

Radio waves from the transmitter reflect off the object and return to the receiver, giving information about the object's location and speed.

Alum is a common alum, potassium aluminum sulphate K2SO4.Al2SO43.24H2O which makes colloidally suspended impurities in water such as clay to settle down.

Deoxyribonucleic acid (DNA) is a nucleic acid polymer composed of monomers called nucleotides. Nucleotides are composed of three components: (1) a pentose sugar; (2) a nitrogenous base; and (3) one to three phosphate groups.

Phoebus Levene, a Russian biochemist was the first to discover the nucleotide and the first to correctly identify the way nucleic acid molecules, DNA.