Physics Forums

Menu
Home
Action
My entries

Defined browse
Select 							   	 					 						Select in the list 						MathematicsPhysics 					 				 				 				Then Select 				 					 						Select in the list 					 					 				 				Then Select 				 					 						Select in the list
Search

photoelectric effect

Definition/Summary
When a metal surface is irradiated, it ejects electrons whose kinetic energy can be measured. This electron emission only happens when the irradiating light is above a certain angular frequency $\omega_{0}$. This frequency threshold is found to be independent of the intensity of the radiation. The kinetic energy of the electrons is found to be linearly related to the frequency of light after the threshold, with $$T = \hbar(\omega - \omega_{0})$$

Equations

Scientists
Einstein

Recent forum threads on photoelectric effect

Breakdown
Physics 					> Quantum 					>> Applications

See Also

Images

Extended explanation
In most elementary courses, the frequency of light is used instead of the angular frequency. The two are related by:  $$\omega = 2\pi \nu$$   The photoelectric effect was important in realising the true nature of light. Classically light is a wave and as such the energy from it should arrive at a uniform rate. In this picture there would be no reason for the electron energy to depend on the frequency and be independent of intensity. This led Einstein to postulate that light was carried in little packets of energy called photons.  The amount of energy needed to overcome the binding energy of the electron in the metal is called the work function ($\phi$). The work function is obviously the same amount of energy as carried by a photon of threshold frequency; $\phi = h\nu_0$. Thus the maximum energy an electron can gain from a photon of energy $E = h\nu$, is:   $$T = h\nu - \phi = h (\nu - \nu_0)$$

Commentary

develish16 @ 10:48 AM Mar23-09
why do i have the feeling that the person who suggested this topic copied the whole content from a high school book without thinking about it for a while. look when it comes to the whole issue of photoelectric effect it is all correct, but when u say that this theory gave the true aspect of light, here u made a mistake.   actually light is a very weird enigma that can solve all the issues of physics if we come up to the right definition of it and its true aspect. when u say that the photons ( i.e. the corpuscular aspect of light) came instead of the wave form, this is wrong!!! till now we only know that each described aspect can be applied to a certain limit ( wave form for explaining diffraction and corpuscular for explaining photoelectric effect). they are both complementary.    but thanks anyway for bringing up this topic. its one of the few that i like the most.

dx @ 09:24 AM May10-08
second sentence, electron spelled wrong.
{"extraction_info": {"found_math": true, "script_math_tex": 0, "script_math_asciimath": 0, "math_annotations": 0, "math_alttext": 0, "mathml": 0, "mathjax_tag": 0, "mathjax_inline_tex": 4, "mathjax_display_tex": 3, "mathjax_asciimath": 0, "img_math": 0, "codecogs_latex": 0, "wp_latex": 0, "mimetex.cgi": 0, "/images/math/codecogs": 0, "mathtex.cgi": 0}, "config": {"markdown_headings": true, "markdown_code": true, "boilerplate_config": {"ratio_threshold": 0.18, "absolute_threshold": 10, "end_threshold": 15, "enable": true}, "remove_buttons": true, "remove_image_figures": true, "remove_link_clusters": true, "table_config": {"min_rows": 2, "min_cols": 3, "format": "github"}, "remove_chinese": true, "remove_edit_buttons": true, "extract_latex": true}, "english_confidence": 0.9275921583175659, "perplexity_flag": "middle"}