Modern Physics
The Photoelectric Effect
What is Modern Physics?
• Modern Physics is what we have discovered
and created in the area of Physics in the last
100 years.
• The Atomic Bomb
• Radiation
• The nature of light (kinda)
Review of Light
• Consider everything you know up until now
about light…
• Is a beam of light an object?
Does it have mass?
Does it have gravity?
Does it have Kinetic Energy?
Review of Light
• Consider everything you know up until now
about light…
• Can light transfer energy?
Increase temp?
Create Electricity?
The nature of light
• Sometimes, light acts just like an object.
• Not a continuous beam, and not a wave.
• When we think of light this way it is called a
PHOHTON (Star Trek- Photon Torpedos…)
Photons
• Photons are little “balls” of light that carry
around energy that can be transferred if the
photon hits something else.
• Photon Symbol:
The structure of an atom
Electron
Energy
Levels
Nucleus
The structure of an atom
Can electrons go from the first energy level to
the second? How?
Electron
Energy
Levels
Nucleus
The structure of an atom
Can electrons go from the first energy level to
the second? How? - It gains energy…
Electron
Energy
Levels
Nucleus
The structure of an atom
Can electrons go from the second energy level
to the first? How?
Electron
Energy
Levels
Nucleus
The structure of an atom
Can electrons go from the second energy level
to the first? How? -It looses energy…
Electron
Energy
Levels
Nucleus
The structure of an atom
What happens to an electron in the outermost
energy level if it gains still more energy?
Electron
Energy
Levels
Nucleus
The structure of an atom
What happens to an electron in the outermost
energy level if it gains still more energy? -Bye!!
Electron
Energy
Levels
Nucleus
The electron is free
from the atom!
The structure of an atom
What is one way electrons can GAIN energy
and go up an energy level?
The structure of an atom
What is one way electrons can GAIN energy
and go up an energy level? -It can get hit by a
Photon!
The structure of an atom
If the photon has enough energy or if the
electron is in the outer level, the electron can
even break free from the atom.
The structure of an atom
What happens if an electron goes down a
level? Where does the lost energy go?
The structure of an atom
What happens if an electron goes down a
level? Where does the lost energy go? -It’s
released in the form of a Photon.
The structure of an atom
If enough photons hit enough atoms, and set
enough electrons free, you get ELECTRICITY!
The structure of an atom
This phenomenon is known as the
PHOTOELECTRIC EFFECT.
The structure of an atom
What is an example of light creating electricity
from the PHOTOELECTRIC EFFECT?
The structure of an atom
What is an example of light creating electricity
from the PHOTOELECTRIC EFFECT?
The Photoelectric Effect
• The photoelectric effect is easiest to observe
though certain METALLIC elements in their
solid form due to their tendency to loose
electrons without a lot of photon energy
present.
Web Simulation
• Complete the Lab Simulation at
www.colorado.phet.edu about the
Photoelectric Effect
+
=