Analyzing this bode plot for frequency break point

bode plotcapacitorresistors

So given this problem:


The correct bode plot for it is:

bode plot

What I don't understand is how the -3db was measured. I know that -3db can be found through 20log(1/sqrt(2)), but how is it measured right at frequency 10kHz?

Best Answer

Be careful, the x-axis is not frequency but radian frequency. So the break-point frequency is not 10 kHz but 10 krad/s.

Now you have the transfer function \$T(\omega)=\dfrac{1}{1+j\omega{}RC}\$ in your top picture. What is the absolute value of that function when \$\omega=1/RC\$?

What is \$1/RC\$ when R is 100 ohms and C is 1 uF?