Questions

Quality of transmission is governed both by nature of signal and nature of communication channel/medium.

Every year 5th September is celebrated as Teacher's Day in India, in the memory of Dr. Sarvepalli Radhakrishnan's birthday. He was the first vice-president and second president of India.

After he become the president of India, his students want to celebrate his birthday in grand but he refused and he adviced them to celebrate that day as teachers day. From then, 5th September is celebrated as Teacher's Day.

In purifying drinking water alum is used for coagulation of mud particles.

DPI [Dots Per Inch] is a measurement of output quality of printer resolution. It represents number of ink dots the printer can place in an area of one square inch. The lesser the DPI the less sharper the image and vice versa.

Therefore, a printer that may have 400 DPI, a printer that can print 400 x 400 per square inch or 1,60,000 dots per inch.

Microwaves are high-frequency signals in the 300 MHz to 300 GHz range. This is in contrast to radio signals, which are typically broadcast in all directions. Radio signals operate in the 3 Hz to 300 MHz range.

Microwave signals are used for both satellite and ground-based communications.

Because the refractive index of glass is highest, light travels slowly in Glass. 

We know that the speed of light depends on the refraction index. The higher the index of refraction is, the slower the speed of light is.

R.I of air and vacuum = 0 (air is a teeny bit more but can be taken as 0)
R.I of water = 1.33
R.I of glass = 1.4.

Hence, Light travels slowest in Glass.