Physics110108: KIm C

Today Ms. K discussed the photoelectric effect and the wave-particle duality.

The Photoelectric Effect

refers to the emission of electrons from the surface of, generally a metal in response to incident light.
particle theory and wave theories of light make different prediction about the effects of the frequency and the intensity of light.
1900 Einstein successfully solved this contradiction when he proposed the idea that light is made up of photons, that interacted with the electrons in the metal like discrete particle,rather than a continous wave.

The Photoelectric Effect and the photocell

Photocell is a vacuum(gaseous pressure of absolute zero) tube with a concave tube called an emitter,made from a material that emits electron easily.
photoelectric effect can be studied using a photocell...

Click the link below for better understanding...

The photoelectric effect and the wave theory

threshold frequency is the minimum frequency of a photon that can eject an electron from a surface.
radiation below the threshold frequency does not eject any electron from the metal no matter how bright it is.
wave theory says that :more intense radiation ,regardless of frequency ,has stronger magnetic and electric fields,the electric field eject the electron from the metal,there should be a delay of seconds before the faint light gained energy to be ejected.
the experiment above (wave theory) was exactly contrast to the experiment of the photoelectric effect.

The photoelectric effect and einstein

Photons is a quantum of light or electromagnetic radiation.
1900 Einstein proposed the idea that light is made up of photon, that interacted with the electrons in the metal like discrete particles,and not continous wave.
his theory explained the existance of threshold frequency.(low frequency , does not have an energy needed to eject electron opposite of high frequency.)
The photon behaves more like a particle than a wave.

The principle of complimentary and light

light behaves both a wave and a particle(wave particle -wave duality)
Niels Bohr clarified this situation by proposing the Principle of complimentary ("to understand a specific experiment ,one must use either the wave or the photon theory but both") the two aspect of light complement each other.
*As a general rule,when light passes through space or through a medium ,its behaviour is best explained using its wave properties.But when light interacts with matter ,its behaviour is more like that of a particle*

homework:

Answer (booklet) # 17-20

next scribe will be ...hmmm.....echizenR18

Physics110108