*_* hi...

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...

http://www.usd.edu/phys/courses/phys431/notes/notes5g/photoelectric.html

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