Questions

It is Blackboard or Chalkboard which is Black when clean, and as you write on it with white chalk it becomes dirty in White color.

RADAR stands for Radio Detection and Ranging.

Radar is a detecting system that uses radio waves to determine the range, angle, or velocity of objects. It operates in the ultra-high-frequency of the radio-frequency (RF) spectrum.

Uses ::

To detect

aircraft,

ships,

spacecraft,

guided missiles,

motor vehicles,

weather formations, and

terrain.

Here the letters follow the rule (AxZ)+(A+Z)

The number corresponding to the letters are used in the rule

A=1, Z=26 => 26x1 + 1 + 26 = 26+27 = 53 =  053

(LxP)+(L+P) = (12 x16) + 12 + 16 = 192+28 = 220

Similarly (11x12) + 11 + 12 => 132 + 23 = 155 

The light from the sun takes about 8 minutes to reach the Earth after it has been emitted from the sun's surface.

The time it takes for light to reach planets in our Solar System varies from about 3 minutes for Mercury to about 5.3 hours for Pluto.

1. Lichens are plants that grow in exposed places such as rocks or tree bark.

2.  Lichens are widely used as environmental indicators or bio-indicators. They can be used as air pollution indicators, especially of the concentration of sulfur-di-oxide in the atmosphere.  

3. They need to be very good at absorbing water and nutrients to grow there.