The equation of a progressive wave is $Y = 3 \sin \left[\pi\left(\dfrac{t}{3} - \dfrac{x}{5}\right) + \dfrac{\pi}{4}\right]$ where X and Y are in metre and time in second. Which of the following is correct?

A source of sound is moving towards a stationary observer with velocity '$V_S$' and then moves away with velocity '$V_S$'. Assume that medium through which the sound waves travel is at rest. If 'V' is the velocity of sound and 'n' is the frequency emitted by the source then the difference between the apparent frequencies heard by the observer is

If the radius of the spherical Gaussian surface is increased then the electric flux due to a point charge enclosed by the surface

The earth is assumed to be a charged conducting sphere having volume 'V' and surface area 'A'. The capacitance of the earth in free space is ($\epsilon_0$ = permittivity of free space)