Term 2 Science ACEwave-particle duality of lightUpdated 2012Copyright Ng Wei Kai (2i1 16)

What is light?• Something to ponder…

“Light is the essence of life, yet it is complicated to understand. The wave-particle duality of light means it possesses both wave-like or particle-like properties."

Light as a form of energy• Allows for the ability to see.• Enables plants to photosynthesize – basic food

source for all other organisms• Without light, there would be very little heat on

earth and the planet will become a dark and barren wasteland which cannot support life.

Wave-particle duality• It is a model to explain how light possesses both

wave-like and particle-like properties.• It only demonstrates what light is like (behavior of

light).• It does not give a specific definition of light.

Light like a wave• Light can be transmitted without a medium as a

wave.• Different Light rays can have different

wavelengths

Light as a particle• Light rays are separated into small, independent

packets of light.• A quantum of light is known as a photon.

(behaves like a particle).

Evidence(s)• The fact that light behaved like particles could be

used to explain a few phenomena in our lives.• One such example would be the photoelectric

effect (discovered by Albert Einstein).

Photoelectric effect• The theory claims that if we have a piece of

matter and we shine light on it, electrons would be emitted.

• This would only happen if the photons comprising of the light ray possessing a minimal level of energy (work function) required for the electrons to be emitted.

• This would not be true if we were to perceive light as possessing wave-like properties.

Experimentation• Double slit experiment• Said to be the “grandfather of Quantum Physics”.• Demonstrates the wave-particle duality.

• Refer to the following YouTube video:• Double slit experiment video

Results• If we were to perform the double slit experiment

using particles, two bands of hits would be formed.

• if we were to perform the experiment using waves, an interference pattern would be observed and multiple bands would be formed.

Results• However, if the experiment is performed using

light, an interference pattern is still observed although the quantum of light, photons, is used.

• This suggests that light might possess both particle-like and wave-like behaviour.

Conclusion• Light possesses both wave-like and particle-like

properties.• However, it is not a wave and neither is it a

particle. • It simply behaves in the same manner.

Bibliography• Classic Two-slit experiment. (2000). University of

California Boulder. Retrieved from http://www.colorado.edu/physics/2000/index.pl.

• Lesson 58: Young's Double Slit Experiment. (n.d.) Mr Clintburg’s StudyPhysics. Retrieved from http://www.studyphysics.ca/

• Double-slit experiment. (n.d.) Hitachi Research and development. Retrieved from http://www.hitachi.com/rd/