Two  waves  of  wavelengths  99 cm   and  100 cm  both  travelling  with  velocity  396 m/s  are  made  to  interfere.  The  of  beats  produced  by  them  per  second  are

For production of beats the two sources must have

In  an  experiment  with  sonometer , a tuning fork  of frequency  with  a  length  of  25 cm  and  another  tuning  fork  resonates  with  a length  of  16 cm.  Tension  of  the  string  remaining  constant  the  frequency  of  the  second  tuning  fork  is

A string is stretched between fixed points separated by 75 cm. It is observed to have resonant frequencies of 420 Hz 315 Hz. There are no other resonant frequencies between these two. Then the lowest resonant frequency for this string is 

Following  two  wave  trains  are  approaching  each  other  y₁  =  a  sin  200  t,  y_{2  =}  a sin  208 t.  The  number  of  beats  heard  per  second  is

The displacement y of a wave travelling in the X-direction is given by

                            y=10^-4 sin (600t -2x +/3).

A  string  in  a  musical  instrument  is  50 cm  long  and  its  fundamental  frequency  is  800 Hz.  If  a  frequency  of  1,000 Hz  is  to  be  produced,  then  required length  of  string  is

A  person  is  standing  on  a  railway  platform  and  a  train  is  approaching  to  him,  what  is  maximum  wavelength  of  sound  he  can  hear  ?  Wavelength  of  whistle  =  1 m,  speed  of  sound  in  air  =  330  m/s,  speed  of  train  =  36  km/h.

The  tension  in  piano  wire  is  10  N.  What  should  be  the  tension  in  the  wire  to  produce  a  note  of  double  the  frequency ?

Two waves are said to be coherent, if they have