In ruby laser, the stimulated emission is due to transition from

In amplitude modulation, the message signal is encoded in the ______ of the carrier wave.

The sky wave propagation is suitable for radio-waves of frequency

If an electromagnetic wave is transmitted to the height equal to 150 km with maximum frequency 300 kHz and critical frequency 100 kHz, the skip distance is

What is the bandwidth of an AM signal if the highest modulating frequency is 5 kHz?

The difference in the refractive index of the fiber core and fiber cladding in step-index fibers is typically

Consider an optical communication system operating at $\lambda \sim 800nm$. Suppose, only 1% of the optical source frequency is the available channel bandwidth for optical communication. How many channels can be accommodated for transmitting audio signals requiring a bandwidth of 8 kHz

Ozone layer blocks the radiations of wavelength

Consider telecommunication through optical fibres. Which of the following statements is no true?

If sky wave with frequency of 50 MHz is incident on D region at an angle of 30°, then angle of refraction is

A laser beam of pulse power ${10^{12}}{\rm{\;W}}$ is focused on an object of area ${10^{ - 4}}\;{\rm{c}}{{\rm{m}}^2}.$ The energy flux in Watt ${\rm{c}}{{\rm{m}}^{ - 2}}$. The energy flux in Watt ${\rm{c}}{{\rm{m}}^{ - 2}}$ at the point of focus is