Yes, F/2 is half the light of F/1.4. But that is only a coincidental thing in this case.
It is because each F/stop is half the light of the one above it and F/2 is the next full stop after F/1.4
From F/1.4 and F/2 the full f/stop numbers alternately double ie next F/stop is 2 x 1.4 = F/2.8, next one after that is 2 x 2 =4.
So listing them.
Each of these F/stops lets in 1/2 a much light as the one above, and twice as much as the one below.
(you will notice a little bit of rounding in the whole numbers)
So, lets assume that we have our ISO and shutter speed that we want to use for a shot. We want it at ISO 100 to reduce noise. We want the shutter speed to be 1/100th of a second for whatever reason.
The camera is currently set on F/4 and there is way too much light.
I turn the dial to F/22 and the image darkens to the correct exposure.
What have we done? How much have we reduced the light?
F/4 to F/5.6 = 1/2, F/5.6 to F/8 = 1/2, F/8 to F/11 = 1/2, F/11 to F/16 = 1/2 and F/16 to F/22 = 1/2.
So all up we have reduced the light by 5 F/stops.
Which is 1/2 x 1/2 x 1/2 x 1/2 x 1/2 = 1/32
By changing from F/4 to F/22 we have reduced the light registering on the sensor to 1/32 of what it was.
How much light is f/2 then? That is exactly how I took it. But when you think about it, f/2 is almost the widest you can go right? F/1.4 being the widest? So it woudn't make sense that f/2 is half the light. Shoot! That sounded so simple to me.