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

Nucleus

ElectronEnergy Levels

The structure of an atom

Nucleus

ElectronEnergy Levels

Can electrons go from the first energy level to the second? How?

The structure of an atom

Nucleus

ElectronEnergy Levels

Can electrons go from the first energy level to the second? How? - It gains energy…

The structure of an atom

Nucleus

ElectronEnergy Levels

Can electrons go from the second energy level to the first? How?

The structure of an atom

Nucleus

ElectronEnergy Levels

Can electrons go from the second energy level to the first? How? -It looses energy…

The structure of an atom

Nucleus

ElectronEnergy Levels

What happens to an electron in the outermost energy level if it gains still more energy?

The structure of an atom

Nucleus

ElectronEnergy Levels

What happens to an electron in the outermost energy level if it gains still more energy? -Bye!!

The electron is free from the atom!

The structure of an atomWhat is one way electrons can GAIN energy and go up an energy level?

The structure of an atomWhat is one way electrons can GAIN energy and go up an energy level? -It can get hit by a Photon!

The structure of an atomIf 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 atomWhat happens if an electron goes down a level? Where does the lost energy go?

The structure of an atomWhat 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 atomIf enough photons hit enough atoms, and set enough electrons free, you get ELECTRICITY!

The structure of an atomThis phenomenon is known as the PHOTOELECTRIC EFFECT.

The structure of an atomWhat is an example of light creating electricity from the PHOTOELECTRIC EFFECT?

The structure of an atomWhat 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

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