The human ear can detect continuous sounds in the frequency range from 20 Hz to 20,000 Hz. Assuming that the speed of sound in air is 330 ms^-1 for all frequencies, calculate the wavelengths corresponding to the given extreme frequencies of the audible range.

An enemy plane is at a distance of 300 km from a radar. In how much time the radar will be able to detect the plane? Take velocity of radio waves as 3 x 10⁸ m s^-1.

Define specific resistance and state it's S.I. unit.

An electric bulb of resistance 500 Ω, draws a current of 0.4 A. Calculate the power of the bulb and the potential difference at it's end.