mariawave: the polaroid ultrasonic rangefinder on a camera sends out a pulse with period 5x10^-7s and wavelengh of 1.5x10^-4m the sound bounces off a unicorn and returns to the camera 0.6s later
Hi Mariawave
Before I forget could I please ask you to give your posts more specific names, it is better for everyone. The right people see your post quicker. You will probably get an answer more quickly and when people search the site for info they find relevant topics more easily.
Now for your question.
You have the period which is seconds/wavelength and you have
Wavelength which is metres/wavelengh.
Now metres/wavelength x wavelengh/second= metres/ second
metres/wavelength ÷ seconds/wavelength = metres/ second
(1.5 x 10^-4) /(5 x 10^-7) m/s
= 0.5 x 10^3 m/s
=5 x 10
2 m/s
=500 metres/sec
500 m/s x 0.6 s
=3000 m
The unicorn is 1.5 km away.
I am writing this on a little phone.
If there's any crazy errors, that is why.
I have now done some corrections
+118654 
