With the function generator
frequency set to 60 Hz or more, the red/green bicolor LED looks the
same as the yellow LED. Decrease
the frequency and it becomes apparent that the LED is a pair of red
and green LEDs alternately flashing. This is also noticeable at
60 Hz if the LED is moved around or if students move their heads.
The color mixing is occurring in the eye of the viewer, due to visual
persistence - the photoreceptors continue to fire for a short time
after the light disappears.
