Consider a circuit consisting of a capacitor $(20 \mu \mathrm{~F})$, resistor $(100 \Omega)$ and two identical diodes as shown in figure. The resistance of diode under forward biasing condition is $10 \Omega$. The time constant of the circuit is $\alpha \times 10^{-3} \mathrm{~s}$. The value of $\alpha$ is $\_\_\_\_$

The voltage and the current between $A$ and $B$ points shown in the circuit are $\_\_\_\_$ .

An unpolarized light is incident on the plane interface of air-dielectric medium shown in figure. If the incident angle is equal to Brewster angle, identify the expression representing reflected wave.

A 1 kg block subjected to two simultaneous forces $(2 \hat{\mathrm{i}}+3 \hat{\mathrm{j}}+4 \hat{\mathrm{k}}) \mathrm{N}$ and $(3 \hat{\mathrm{i}}-\hat{\mathrm{j}}-2 \hat{\mathrm{k}}) \mathrm{N}$ is moved a distance of 25 m along $(3 \hat{\mathrm{i}}-4 \hat{\mathrm{j}})$ direction. The work done in this process is $\_\_\_\_$ J.