Questions in waves

Select	Question
	The relation between phase difference ($\Delta \varphi$) and path difference ($\Delta x$) is
	A hospital uses an ultrasonic scanner to locate tumours in a tissue. The operating frequency of the scanner is 4.2 MHz. The speed of sound in a tissue is 1.7 km/s. The wavelength of sound in the tissue is close to
	The minimum audible wavelength at room temperature is about
	The ratio of the speed of sound in nitrogen gas to that in helium gas, at 300 K is
	In a sinusoidal wave, the time required for a particular point to move from maximum displacement to zero displacement is 0.170 second. The frequency of the wave is
	The number of waves contained in unit length of the medium is called
	The frequency of a rod is $200 Hz$. If the velocity of sound in air is $340\,m{{s}^{-1}}$, the wavelength of the sound produced is
	Frequency range of the audible sounds is
	In a medium sound travels 2 km in 3 sec and in air, it travels 3 km in 10 sec. The ratio of the wavelengths of sound in the two media is
	A stone is dropped into a lake from a tower 500 metre high. The sound of the splash will be heard by the man approximately after