thanks Bernard green, for your well explained article, but we can all go on arguing about things, so first of all yes the LED is a current device, in other words it starts to emit light. Its colour is determined by its wavelengths Different materials and processes determine what colour it will produce.
Its brightness depends on how much current is being pushed or driven through it, However there are other methods that can control its brightness. and that is true, if one wants to argue about this then get onto do an experiment to confirm this. I deal with thousands of different types of LEDs, in Multiplexed signs, we control intensity by pushing through 10 times more current for a brief period to make up for loss of intensity due to Multiplexing, which has same effect as PWM.
As for Peak v/s RMS, In Britain we get 230V ac that everyone knows, but of course most people don't know that it is actually 325V peak to peak, but we say it is 230v because that has same effect as a steady 230v DC.
So the true peak or potential of our power supply is in fact 325-330V, highly dangerous, but we call it 230V because it is in a sine wave format, which means it is not a steady 325-330V so being a sine wave in nature, we realised that it has the same power effect as 230V DC supply.
So we worked out that it is approx 0.7 times the peak value and we get a net or RMS as being 230V.
I am trying to explain to someone who asked what is a leading edge and a trailing edge. not giving him a lecture on how to work out a Peak Voltage of an RMS waveform, I know that a peak voltage is 1.414 x the RMS (Root Mean Square) so I was trying to explain that in terms of an AC cycle the peak (not the peak voltage) but the peak direction of the voltage, so in other words I was trying to say when the wave reaches the upmost positive level or peak, it is at 90 degrees, and at that level the voltage is 230V (RMS) same as we don't say that we get 325V AC in our homes! We all know what we get in our homes, and everyone refers to it as 230V AC, what I said was when the rising voltage reaches the peak, the starts to climb down, I am explaining a waveform and leading edge and trailing edge, not trying to confuse him with peak voltage and RMS voltage.