Wavelength And Frequency

A source of unknown frequency gives 4 beats/s, when sounded with a source of known frequency 250 Hz. The second harmonic of the source of unknown frequency gives five beats per second, when sounded with a source of frequency 513 Hz. The unknown frequency is

The power radiated by a black body is P and it radiates maximum energy at wavelength, \lambda ₀ . If the temperature of the black body is now changed so that it radiates maximum energy at wavelength , the power radiated by it becomes nP. The value of n is