6.2 The Photoelectric Effect Flashcards
Photoelectric effect
Occurs when light energy contacts a metal and releases electrons from the metal.
One electron is liberated from the metal surface for every photon absorbed.
In order for the electrons to leave the metal a photon must have enough energy to knock it put of its position around the metal nuclei.
If energy is too low, an electron will not be emitted
The brighter the light, the more photons hit the metal and therefore more electrons are liberated as long as the photons have enough energy
What is a phototube?
Two parallel plates enclosed in an evacuated glass tube.
Draw Milikan’s Apparatus
Page 257
Describe the photoelectric effect
- light illuminates a metal surface, and electrons are enjoyed immediately
- each metal has its own threshold frequency where electronics are elites only at certain frequency or above
- when EMR is at or above the threshold frequency the ENERGY of emitted electrons will increase as the FREQUENCY of the incident EMR increases
- when the INTENSITY of light is increased, the CURRENT of electrons will increase. (If above threshold frequency)
Photoelectron
The electron that is released from the photoelectric effect.
The photoelectric effect may be explained using the particle model of light in conjunction with the Law of Conservation of Energy.
Photon energy = kinetic energy of the electron + work function
Draw a photoelectric graph
Page 258
At the threshold frequency the energy of the photon is equal to the work function so the kinetic energy of the photon electron is?
Zero
Draw a photoelectric Apparatus with a voltmeter and ammeter and label.
Page 266
Photocurrent
The flow of electric charge in a photoelectric cell.
Photoelectron
An electron ejected out of a metal (photoelectric metal) by an incoming photon that had enough energy to knock it out its position.
Explain how the photoelectric effect supports the particle nature of light
The photoelectric effect can be better explained using the concept of light being a particle rather than light being a wave. A wave could release electrons by hearing the metal, but not instantaneous; a collision between particles could be an instantaneous release if the energy of the particle is greater than the work required to release the electron.
In the equation for the photoelectric effect, the expression “max kinetic energy” is used. Explain the use of the word “maximum”.
It only deals with surface electrons as compared to those electrons located nearer to the nucleus of the photoelectric element.
Milikan’s apparatus
Photoelectric effect
