Estimate the approximate volume of aluminium nucleus $(A=27)$, use $\binom{R_0 \simeq 1.0 \times 10^{-15} \mathrm{~m}}{\pi \simeq 3}$

A $p-n$ junction is fabricated from a semiconductor with band gap of 2.8 eV . what approximate wavelength it cannot detect? [Use, $h=6 \times 10^{-34} \mathrm{~m}^2 \mathrm{~kg} / \mathrm{s}$ ]

Identify the logic operation performed by the following circuit.

A carrier wave of peak voltage 10 V is used to transmit a message signal. What should be the peak voltage of the modulating signal in order to have a modulation index of $80 \%$ ?