Einstein and the Photoelectric Effect lesson illustration

 

What color is a very hot
object in Infrared?

Man tossing hot and cold water balloons
(thermal infrared!)

School Blocks YouTube? Click on video link below

Video

 

 

B) Einstein explains photoelectric effect

 

 

1) Light intensity and electron emission explained.

 

 

Photons are received individually
Einstein and the Photoelectric Effect lesson illustration
Each photon emits e -  

 

 

Light emitted as particles
(quanta of light - photon)

 

 

Bright Light

 

 

 Dim Light

Einstein and the Photoelectric Effect lesson illustration

Einstein and the Photoelectric Effect lesson illustration

(Lots of photons)

 (few photons)

 

 

 

 

High Frequency Light

Low Frequency Light

Einstein and the Photoelectric Effect lesson illustration

Einstein and the Photoelectric Effect lesson illustration

(High Energy Photons)

(Low Energy Photons)

 

 

 

 

Brightness (Intensity) - measure of # of photons emitted.

 

 

Frequency measure of energy of light
 

Einstein and the Photoelectric Effect lesson illustration

Photon Energy = 5 eV

KE = 2 eV

 

 

 

**eV - electron volts - unit of energy

 

 

 

 

 

How much work did this photon have to do to remove the electron? 

 

 

 

Answer: 3 eV

 

 

 

 

 

What would happen if a photon
 of 2 eV hit the same metal?

 

Einstein and the Photoelectric Effect lesson illustration
Photon Energy = 5 eV KE = 2 eV

 

 

 

 

Photon would not have enough energy to emit an electron

Einstein and the Photoelectric Effect lesson illustration
Photon Energy = 5 eV KE = 2 eV

 

 

 

Einstein and the Photoelectric Effect lesson illustrationEmax = hf - WoEinstein and the Photoelectric Effect lesson illustration