Given
frequency of laser beam is   f = 4.4
*1014 Hz
wave length of laser beam is
             Â
? = c  /f
                  Â
= ( 3 *108 m/s ) / ( 4.4*1014 Hz )
                  Â
= 6.82*10-7Â Â m
pulse emit by laser is
          T =
2.1*10-6 s
  total wave length of the pulse
          ?'
=  c  /f Â
              Â
= c T
              Â
= ( 3*108 m/s ) (2.1*10-6 s )
               Â
= 630 m
number of wave lengths
           Â
n =Â Â ?'Â Â Â / ?
               Â
= 630 / 6.82*10-7Â Â
                Â
= 9.237*108Â Â
