# Homework Help: Beat frequency of strobe lights

1. Apr 7, 2009

### begbeg42

1. The problem statement, all variables and given/known data
The strobe lights on top of two tall radio towers both have a period of about 1.00 s. When turned on simultaneously, a keen observer notes that during an 813 s interval, the lights gradually fall out of synchronization and then come back into flashing synchronously. What is the interval ΔT between the periods of the two beacons?

2. Relevant equations

abs(frequency1-frequency2)=beat frequency

3. The attempt at a solution
it would appear that the two strobe lights have the same frequency, frequency=1/period=1 Hz...I dont know what to make of the 813 interval or what exactly delta-T refers to physically

I know the beat frequency involves the superimposition of these two light waves...

2. Apr 7, 2009

### begbeg42

i have
299,792,458 m/s=speed of light=frequency(wavelength)
is this relevant?

also is the frequency in this time interval 813 Hz? the period is 1 s i.e. the light completes an oscillation every second so in a 813 s time interval there 813 oscillations?

i know that initially f1-f2=0
then abs(f1-f2) doesn't = 0
then it does again....
however im not sure what delta-T refers to/asks for... and not sure how to work this

3. Apr 7, 2009