PYQs Based Test - 09 : Communication and Optical Instrumentation

An optical pulse containing 6 × 10⁶ photons is incident on a photodiode and 4.5 × 10⁶ electron-hole pairs are created. The maximum possible quantum efficiency (in %) of the photodiode______.

An amplitude modulated signal is shown in the figure. The Modulation index is (up to one decimal place) _______.

A signal having a bandwidth of 5 MHz is transmitted using the Pulse code modulation (PCM) scheme as follows. The signal is sampled at a rate of 50% above the Nyquist rate and quantized into 256 levels. The binary pulse rate of the PCM signal in Mbits per second is ___.

A laser pulse is sent from ground level to the bottom of a concrete water tank at normal incidence. The tank is filled with water up to 2 m below the ground level. The reflected pulse from the bottom of the tank travels back and hits the detector. The round-trip time elapsed between sending the laser pulse, the pulse hitting the bottom of the tank, reflecting back and sensed by the detector is 100 ns. The depth of the tank from ground level marked as x in metre is ____.
(Refractive index of water n${}_{water}$ = 1.3 and velocity of light in air cₐᵢᵣ = 3 × 10⁸m/s)

As shown in the figure, a slab of finite thickness t with refractive index n₂ = 1.5, has air (n₁ = 1) above and below it. Light of free space wavelength 600 mm is incident normally from air as shown. For a destructive interference to be observed at R, the minimum value of the thickness of the slab t(in mm) is ______