If m is the mass of an electron and c is the speed of light, the ratio of the wavelength of a photon of energy E to that of the electron of the same energy is

• $\mathrm{c}\sqrt{\frac{2\mathrm{m}}{\mathrm{E}}}$

• $\sqrt{\frac{2\mathrm{m}}{\mathrm{E}}}$

• $\sqrt{\frac{2\mathrm{m}}{\mathrm{cE}}}$

• $\sqrt{\frac{\mathrm{m}}{\mathrm{E}}}$

The set which represents the isotope, isobar and isotone respectively is

• (₁H², ₁H³), (₇₉Au197, ₈₀Hg¹⁹⁸) and (₂He³, ₁H²)

• ( ₂He³, ₁H¹), (₇₉Au¹⁹⁷, ₈₀Hg¹⁹⁸) and (₁H¹, ₁H³)

• (₂He³, ₁H³), (₁H², ₁H³) and ( ₇₉Au¹⁹⁷, ₈₀Hg¹⁹⁸)

• (₁H², ₁H³), (₂He³, ₁H³) and (₇₉Au¹⁹⁷, ₈₀Hg¹⁹⁸)

Two samples X and Y contain equal amount of radioactive substances. If $\frac{1}{16}$th of the sample X and $\frac{1}{256}$th of the sample Y, remain after 8 h, then the ratio of half periods of X and Y is

• 2 : 1

• 1 : 2

• 1 : 4

• 1 : 16

Radioactive ${}_{27}{}^{60}\mathrm{Co}$ is transformed into stable ${}_{28}{}^{60}\mathrm{Ni}$ by emitting two γ-rays of energies

• 1.33 MeV and 1.17 MeV in succession

• 1.17 MeV and 1.33 MeV in succession

• 1.37 MeV and 1.13 MeV in succession

• 1.13 MeV and 1.37 MeV in succession

A pure semiconductor has equal electron and hole concentration of 1O¹⁶ m^-3. Doping by indium increases n_h to 5 x 10²² m^-3. Then, the value of n_e in the doped semiconductor is

• 10⁶ /m³

• 10²² /m³

• 2 × 10⁹ / m³

• 10¹⁹ /m³

The collector supply voltage is 6 V and the voltage drop across a resistor of 6OO Ω in the collector circuit is 0.6 V, in a transistor connected in common emitter mode. If the current gain is 20, the base current is

• 0.25 mA

• 0.05 mA

• 0.12 mA

• 0.02 mA

A full-wave rectifier circuit with an AC input is shown

The output voltage across R_L is represented as

A carrier frequency of 1 MHz and peak value of 10 V is amplitude modulated with a signal frequency of 10 kHz with peak value of 0.5 V. Then the modulation index and the side band frequencies respectively are

• 0.05 and ± 0.010 MHz

• 0.5 and 1 ± 0.010 MHz

• 0.05 and 1 ± 0.005 MHz

• 0.5 and 1 ± 0.005 MHz

The maximum line-of-sight distance d_M, between two antennas having heights h_T and h_R above the earth is

• $\sqrt{\mathrm{R} ({\mathrm{h}}_{\mathrm{T}} + {\mathrm{h}}_{\mathrm{R}})}$

• $\sqrt{2\mathrm{R}/\left({\mathrm{h}}_{\mathrm{T}} + {\mathrm{h}}_{\mathrm{R}}\right)}$

• $\sqrt{{\mathrm{Rh}}_{\mathrm{T}}} + \sqrt{2{\mathrm{Rh}}_{\mathrm{R}}}$

• $\sqrt{2{\mathrm{Rh}}_{\mathrm{T}}} + \sqrt{2{\mathrm{Rh}}_{\mathrm{R}}}$

70.

The frequency band used in the downlink of satellite communication is

• 9.5 to 2.5 GHz

• 896 to 901 MHz

• 3.7 to 4.2 GHz

• 840 to 935 MHz