Question

What is the ratio of focal length to diameter for practical applications in a parabolic reflector?

(a) 0.25 to 0.5

(b) < 0.25

(c) 0.125 to 0.3

(d) 0.5 to 1

The question was asked in my homework.

This is a very interesting question from Parabolic Reflector Antenna topic in division Reflector Antenna of Antennas

Answer 1

The correct answer is (a) 0.25 to 0.5

Best explanation: The ratio of focal length (f) to diameter (d) f/d < \(\frac{1}{4}\) indicates radiation away from the parabolic surface of the reflector.  So for practical applications it lies between 0.125 and 0.5.