C. PWM. Isn't normal PWM at 490-500 Hz? Can you see that flickering? I thought above 24H the brain put it together as steady. Good computer monitors used to go 60Hz, maybe 72. 500 for an LED would seem sufficient.
White ø 5mm Clear LED Extra Bright 20,000mcd - dipmicro electronics $0.26
Shipping $2.50
Get some other stuff at the same time, the price really drops with at qty 4 and then again at 10.
1 = 26 cents. 4 = 63 cents total. 10 = 94 cents total. 20 = $1.47 total.
Get some other colors for your next project!
You run one of these bad boys at 20mA, will seem omnidirectional it is so bright! I've read if you lightly sand the outside to diffuse it, will seem even more so.