Why is it that different coloured LED's have different rates of switching on and off?

i have tried very hard to find the answer via research on the internet, visited many sites about LED's, but have been unable to find out the answer to this question.

so of course anybody who could explain it, or post a link to a website which does, it would be greatly appreciated.
thank you.

 

what do you mean by rates of switching.
You can find answers only if your question makes sense.

 

thanks for replying. well i mean exactly that, the speed at which the LED flicks on and flicks off. so how soon after getting electricity does the LED turn on. so why is it that when in an exact same astable multivibrator circuit do green LEDs flicker faster than red LEDs

 

Post the circuit and perhaps we can tell.

 

They dont. The switching speed is not a cause for flicker. It is the duty cycle.

You want to look at the datasheets for your different color LEDs. They have different Vf (forward voltage, or voltage drop) and some require more current to appear as bright.

You may not want to use the same astable mv for both leds, as they may require different operating voltages or current. If you found a green and red LED of the same specs, there would be no difference (noticiable. A few nM of wavelength maybe) It could also be your eyes ability to perceive color.

 

LEDs respond to current, they do not control it. Their may be minor speed differences, but given that LEDs are meant to provide light typically for humans, who can't tell 1 or 2 milliseconds apart, 1 or 2 nano or microseconds doesn't mean squat. My feeling is the questions is meaningless.

If an LED is fed DC it doesn't flick on or off, it provides continuous light.

LEDs, 555s, Flashers, and Light Chasers

 

I'm guessing that the LED is part of the multivibrator circuit and so the different forward voltages change it's frequency.
Post the circuit.

 

thanks for all the replies
the circuit is the same as this one, except that there is a LED after resistor 1 and another LED after resistor 4.

cant get the image thing to work, so here is the link
http://upload.wikimedia.org/wikipedia/commons/6/6a/Transistor_Multivibrator.svg

 

the capacitors will charge at different rates after the LEDs. This is due to the different voltage drops from the different LEDs.

 

oh that is so obvious, i can't believe i didn't figure that out. im so ashamed lol. thanks a lot for the help