Photoelectric effect Flashcards
1
Q
What is a photon
A
A packet of light energy
2
Q
What is the photoelectric effect
A
Release of electrons from a surface of a metal when exposed to U.V light above a certain frequency
3
Q
Describe the experiment to demonstrate the photoelectric effect
A
- Stand a piece of zinc and place it on the cap of the electroscope
- Negatively charge the electroscope by induction
- Shine U.V light on the cap
4
Q
Result of the photoelectric effect experiment
A
Negatively charged electroscope: Leaves collapsed
Positive electroscope: Leaves diverge further
Repeat using infra-red
5
Q
What was observed when infrared radiation was used
A
Leaves did not collapse
- Frequency of light is too low to displace the electrons
6
Q
Describe how the electroscope was charged negatively
A
By induction
. a positively charged rod is held close to the cap of the electroscope
. Place a finger on the cap
7
Q
One application of the photoelectric effect
A
Security alarms
