The velocity of waves having wavelength 0.643 m and frequency 3.25 e 10 hz is

The relationship between velocity (v), wavelength (w) and frequency (f) is expressed as:

v = w f

Plugging in the given values into the equation:

v = 0.643 m (3.25 e 10 Hz)

Where Hz = 1 / s , therefore:

v = 0.643 m (3.25 e 10 / s)

v = 2.09 e 10 m / s

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.