Have you ever wondered why the aperture number skip in such a weird way? What does 1.4 has to do with 2? The video below by Dylan Bennett has a great primer on the relations between focal length, aperture and the amount of light hitting the sensor.
My favorite part is the trick to remember aperture stops -> Start with 1.4 and 2. and then double the numbers for the next stop => 1.4, 2, 1.4×2=2.8, 2×2=4, 2.8×2=5.6, 4×2=8 and so on.
A Simple Explanation of F-Stop | Dylan Bennett
Thanks for the tip, Brian.