$9 imes {10^{17}}$

$3 imes {10^{16}}$

$9 imes {10^{15}}$

$3 imes {10^{19}}$

${h^{1/2}}$

$h$

${h^3}$

${h^2}$

$\sim 1.2\; imes {10^{12}}\;{{\rm{m}}^{ - 3}}$

$\sim \;{10^6}\;{{\rm{m}}^{ - 3}}$

$\sim \;{10^{14}}\;{{\rm{m}}^{ - 3}}$

$\sim \;{10^{22}}\;{{\rm{m}}^{ - 3}}$

Active Medium

Reflective Cavity

Output Coupler

Pumping Source

32000 bits/s

16000 bits/s

64000 bits/s

72000 bits/s

Ground state to excited state

Metastable state to ground state

Excited state to metastable state

Excited state to ground state

Visible light

Infrared

Ultraviolet

Microwave

An amplifier

A mixer

A frequency separator

A phase separator

Critical Frequency

Maximum Usable Frequency

Optimum Working Frequency

Skip Frequency

Only television communication

Can be reflected by ionosphere

Cannot be reflected by mesosphere

Cannot be reflected by any layer of earth's atmosphere

Less than $3 imes {10^{ - 7}}{\rm{\;m}}$

Equal to $3 imes {10^{ - 7}}{\rm{\;m}}$

More than $3 imes {10^{ - 7}}{\rm{\;m}}$

All of these