Surface tension and doppler effect in sound and light ..! help plz

[Physicist N]

Alsalamu Alaikum w rahmato Allah w barakatoh

Dear Physicist :
first i want to say that am sooo happy to find this forum about physics<3
also i want to thank all the people here for their efforts ..... : )

well..
i have a project in the university about surface tension
our goal is to measure the theta of different kind of oils
by using 1.calculation(theoretically) , 2. Experimentally
we put different types of oil in a tube with diameter 0.5cm
and capture it ...
now my questions are :
1. Do u have any idea how to measure the theta by using simple equipment???
2. i found the density for the oils from the internet ( so am not sure about them !)
then measure the value of the tension by using the equation
T=1/(2dgr(h+1/3r)) ... then subsisting T in the equation Cosθ= rdgh/2T
but i couldn’t find the theta .. i don’t know why ??!! i got math error (more then 1 or less than -1 )
so i want to know whats my mistake here ????


Also , i need a summery or simple power point about doppler effect in sound and light please

Note: I know Arabic well in case you know the answer and can’t explain it to me , please feel free to write it in Arabic

Thank you very much for your time
best regards


Physicist N