An individual white led (light-emitting diode) has an efficiency of 20% and uses 1.0 w of electric power. a. how many leds must be combined into one light source to give a total of 1.6 w of visible-light output (comparable to the light output of a 40 w incandescent bulb)? b. what total power is necessary to run this led light source?

8, 8 W

Explanation:

The useful power of 1 Light Emitting Diode is

Total power required is 1.6 W

Number of Light Emitting Diodes would be

The number of Light Emitting Diodes is 8.

Power would be

The power that is required to run the Light Emitting Diodes is 8 W

when heated, the valance electrons increased their speed and transferred the heat from electron to electron.   i just took the test.

the answer is 12 as i may remember

: )