I asked twice and got no answers =( Please help ME!!!!?

Question

1. What is the period of a 560 Hz sound wave in air?

2. While riding in your boat, you notice one wave pass by every two seconds. If the actual frequency of the waves is

1 Hz, with what speed are you moving through the water?

(The speed of the wave is 5 m/sec)

Answer 1

1.the frequency of a wave is defined as the reciprocal of it's time period of propagation.if the frequency is 560Hz,the period is1/frequency=1/560Hz=1.7857Milli seconds.

2.this is based on the principle of Doppler effect ,meaning that the frequency received is different from the actual frequency due to relative motion of the observing frames.here the source (the wave)and the  the observer are moving away from each other.therefore the Doppler effect in consideration is relativistic.here let the relativistic velocity be positive and have the value v.first we solve for v and then solve for the speed of the boat depending on the sign of v.

the formula is:f(observed)=sq root((1-(v/speed of light))/(1+(v/speed of light)))*frequency of emitted wave.

here frequency of emitted wave =1/time period=1/2s=0.5Hz.

f(observed)=1 Hz.c=5m/s..

solving for v we get:v=-3m/s.

however this is the relative velocity of the boat with respect to the wave.relative velocity =velocity of boat -velocity of wave.therefore velocity of boat=-3m/s-5m/s=-8m/s=8m/s in the negative x-direction.

Answer 2

in question #1 the period would be equal to  0.0017857

solution:

f = 1/T

where f  = is frequency

where T = is the period

if we derive the formula f = 1/T

the formula for period would be T = 1/f

T = 1/560hz = 0.0017857

question#2 give a minute :)

Answer 3

1. T = 1/f

2.You must be moving along in the same direction as the waves, at half their speed.