Assertion: In high latitudes one sees colourful curtains of light hanging down from high altitudes. 

Reason: The high energy charged particles from the are deflected to polar regions by the magnetic field of the earth.

• if both assertion and reason are true and the reason is the correct explanation of the assertion

• if both assertion and reason are true and the reason is not the correct explanation of the assertion

• if assertion is true but reason is false

• if both assertion and reason are false statements

High-frequency waves are

• affected by the solar cycle

• reflected by ${\mathrm{D}}_2$ layer

• absorbed by the ${\mathrm{F}}_2$

• capable of use for long-distance communication on the moon

73.

The principle of LASER action involves

• amplification of particular frequency emitted by the system

• population inversion

• stimulated emission

• All of the above

Through which mode of propagation, the radio waves can be sent from one place to another?

• Ground wave propagation

• Sky wave propagation

• Space wave propagation

• All of the above

The binary number 10111 is equivalent to the decimal number

• 19

• 31

• 23

• 22

To write the decimal number 37 in binary, how many binary digits are required ?

• 5

• 6

• 7

• 4

The decimal equivalent of the binary number (11010.101)₂ is 

• 9.625

• 25.265

• 26.625

• 26.265

The decimal number equivalent to a binary number 1011001 is

• 13

• 17

• 89

• 178