Physics HELP!!
posted by joane .
a). What is the wavelengh of a 2.54MHz ultrasound wave travelling through aluminum?(the speed of sound in aluminum is 6420 m/s)
b). What frequency of electromagnetic wave would have the same wavelength as the ultrasound wave above?

a) frequency x wavelength = (wave speed)
2.54*10^6 * wavelength = 6420 m/s
Solve for the wavelength
b) Use the same formula, but with 3.00*10^8 m/s (the "speed of light") for the wave speed, and the previous answer for the wavelength. 
I am not getting the right answer for part b !
I don't know why though! :( 
How much current is required to produce a force of 0.96 N on a 75 cm long wire oriented at right angles to a 0.24 T magnetic field?