Wave and Particle Duality
In order to accept Quantum theory a thorough understanding of light and its nature must be understood. The unusual phenomenon of light is that it acts as both a wave and a particle (Think quest 2012, p. 1). Through the use of the photoelectric effect light’s particle properties are observed. The photoelectric effect is an experiment where light is shone on a metallic surface, in this case sodium metal and as a result electrons are produced (Nave 2000, p. 3). These ejected electrons were measured as an electric current. The voltage was then derived and hence the maximum kinetic energy (volts) was calculated (Nave 2011, p. 3).
The data clearly shows a directly proportional relationship between the ejected electrons energy and the frequency of the light indicating a particle nature. This data coincided with Planck’s previous hypothesis that, “vibrating molecules emitting the radiation could have only certain discrete amounts of energy” (Cliff’s notes 2012, p. 2), which is evident in the expression; (Where h is Planck’s constant 6 .626 x 10-34 and v is the velocity (ms-1)). Thus from this expression it is evident that light acts as a particle. However DeBroglie proposed that light could also act as a wave by manipulating the expressions of Einstein’s special relativity and Planck’s hypothesis from the photoelectric effect.
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This enables the momentum of a photon to be calculated, indicating a wave-like behaviour. Davisson and Germer later supported this theory through an experiment where light was directed onto a metal crystal, in this case nickel. The results showed that the light scattered and hence diffracted indicating obvious wave-like properties (Nave 2011, p.4). Hence light was acknowledged to act as both a wave and particle, which is imperative in quantum mechanics as light is at the focus of this phenomenon.
References
Cliffs notes 2012, “Modern physics”, Wiley and sons Inc., viewed 13th October 2012, <www.cliffsnotes.com/studyguide/Relativity.topicArticleId-10453,articleId-10445.html>
Nave 2011, “Wave-particle duality”, viewed 14th October 2012, < http://hyperphysics.phy-astr.gsu.edu/hbase/mod1.html#c5>
Think Quest 2012, “What is Quantum physics?”, library think quest, viewed 24th September 2012, <www.library.thinkquest.org/3487/qp.html>
Nave 2011, “Wave-particle duality”, viewed 14th October 2012, < http://hyperphysics.phy-astr.gsu.edu/hbase/mod1.html#c5>
Think Quest 2012, “What is Quantum physics?”, library think quest, viewed 24th September 2012, <www.library.thinkquest.org/3487/qp.html>