Modern Physics >
Quantum Effects > Photoelectric Effect |
DCS# 7A10.15 |
PHOTOELECTRIC
EFFECT WITH A NEON BULB
APPARATUS
neon bulb
|
202-13-A2 |
set
of colored LEDs with batteries
|
202-21-G6 |
resistor
|
214-01-A
|
100 V DC power supply
|
202-08-E |
momentary SPDT switch
|
101-09-D5 |
DESCRIPTION
The power supply voltage applied
to the neon bulb is just below the threshold necessary for the
bulb to light, about 74 V. Shining a green laser, a blue
or uv LED on the bulb will cause it to glow, as electrons are
ejected from the metal electrodes and the bulb becomes
conducting, but a red laser and yellow LED will not. The
bulb extinction voltage is about 65 V, so the switch is used to
open the circuit and extinguish the bulb between trials.
NOTES
The decade resistor should be set
to 500 ohms. The switch should be connected so that it the
circuit is normally closed.
REFERENCE
The
Physics Teacher 44, 310 (2006).