two friends at different locations want to communicate with each other by sending low energy signals. which of the following methods can they use to communicate?

a) produce x‒rays using colliding electrons and send them to radios, which capture sound.

b) send messages using infrared radiations, which travel in the form of waves.

c) send radio waves through intervening media like radio and television.

d) produce sound waves using microwaves from heated objects.

the answer is C. Send radio waves through intervening media like radio and television.

this is because you cant hear voices through infrared waves, x-rays, and heating up objects. that make no sense.

a mercury barometer is a device that uses the physical properties of mercury in a tube to measure barometric pressure. mercury barometers are used for : -

1. measurement of atmospheric pressure  

2. determining the altitude of a place

3. weather forecasting

4. calibration and checking of aneroid barometers

5. application in fluid mechanics

6. measurement of pressure in aircrafts

7. surface weather analysis

8. preparation of barographs

9. usage in physical sciences like physics, astronomy & chemistry

10. preparation of aircraft altimeters

characteristics of mercury barometer : -

1.used to define and measure atmospheric pressure.

2.on the average at sea level the column of mercury rises to a height of about 760 mm.

3.this quantity is equal to 1 atmosphere.

4.it is also known as standard atmospheric pressure.

5.a barometer in which the weight of a column of mercury in a glass tube with a sealed top is balanced against that of the atmosphere pressing on an exposed cistern of mercury at the base of the mercury column, the height of the column varying with atmospheric pressure.

the answer would be a