A Young's double-slit experiment is performed using monochromatic light of wavelength $$\lambda $$. The intensity of light at a point on the screen, where the path difference is $$\lambda $$, is K units. The intensity of light at a point where the path difference is $${\lambda \over 6}$$ is given by $${{nK} \over {12}}$$, where n is an integer. The value of n is __________.

The output characteristics of a transistor is shown in the figure.
When V_CE is 10V and I_C = 4.0 mA, then value of $$\beta $$_ac is __________.

In a series LR circuit, power of 400W is dissipated from a source of 250 V, 50 Hz. The power factor of the circuit is 0.8. In order to bring the power factor to unity, a capacitor of value C is added in series to the L and R. Taking the value of C as $$\left( {{n \over {3\pi }}} \right)$$ $$\mu $$F, then value of n is __________.

An engine operates by taking a monoatomic ideal gas through the cycle shown in the figure. The percentage efficiency of the engine is close to __________.