Assertion : The electrical conductivity of earth's atmosphere increases with altitude.

Reason : The high energy particles (i.e., y-rays and cosmic rays) coming from outer space while entering our earth's atmosphere cause ionization of the atoms of the gases present in the atmosphere and their energy decreases as they approach to earth and so closes ion charge density

Assertion : Surface wave and sky wave can not be observed on moon.

Reason : Atmosphere of variable refractive index is required for propagation of surface & sky wave

Assertion: Diode lasers are used as optical sources in optical communication.

Reason: Diode lasers consume less energy.

Assertion: Short wave bands are used for transmission of radio waves to a large distance.

Reason: Short waves are reflected by ionosphere.

A diode detector is used to detect an amplitude modulated wave of $60\%$ modulation by using a condenser of capacity $250 \mathrm{pF}$ in parallel with a load resistance $100 \mathrm{k\Omega }$. Find the maximum modulated frequency which could be detected by it.

In amplitude modulation, the sinusoidal carrier frequency used is denoted by $\omega_{\rm{c}}$ and the signal frequency is denoted by ${\omega }_{\mathrm{m}}$. The bandwidth $\left(\Delta {\omega }_{\mathrm{m}}\right)$ of the signal is such that $\Delta {\omega }_{\mathrm{m}}\ll {\omega }_{\mathrm{c}}$. Which of the following frequencies is not contained in the modulated wave?