PHYSICS 7E Lecture Notes - Lecture 15: Christiaan Huygens, Electromagnetic Radiation, Black Body
PHYSICS 7E - Lecture 15 - Electromagnetic Waves / The Nature of Light
*Images from University Physics, Young & Freedman
Momentum
●Electromagnetic waves transport momentum as well as energy
●As this momentum is absorbed by some surface, pressure is exerted on the surface
●Assuming the wave transports a total energy U to the surface in a time interval , thetΔ
total momentum is for complete absorption/cp =U
Pressure and Momentum
●Pressure, p, is defined as the force per unit area
/Cpav =Sav
●For complete absorption
●An absorbing surface for which all the incident energy is absorbed is called a
black body
S/Cpav = 2 av
●For complete reflection
The Nature of Light
●Before the beginning of the nineteenth century, light was considered to be a stream of
particles
●Christiaan Huygens argued that light might be some sort of a wave motion
●Maxwell asserted that light was a form of high-frequency electromagnetic wave
○Thomas Young (1801) provided the first clear demonstration of the wave nature
of light
●Einstein (in 1905) proposed an explanation of the photoelectric effect that used the idea
of quantization:
○Dual Nature of Light, photons, E=hf
The Nature of Light
●Light has properties of both waves and particles. The
wave model is easier for explaining propagation, but
some other behavior requires the particle model
●The rays are perpendicular to the wave fronts
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Document Summary
Physics 7e - lecture 15 - electromagnetic waves / the nature of light. Electromagnetic waves transport momentum as well as energy. As this momentum is absorbed by some surface, pressure is exerted on the surface. Assuming the wave transports a total energy u to the surface in a time interval t . , the total momentum is p = u. Pressure, p, is defined as the force per unit area. An absorbing surface for which all the incident energy is absorbed is called a black body pav = 2 av. Before the beginning of the nineteenth century, light was considered to be a stream of particles. Christiaan huygens argued that light might be some sort of a wave motion. Maxwell asserted that light was a form of high-frequency electromagnetic wave. Thomas young (1801) provided the first clear demonstration of the wave nature of light. Einstein (in 1905) proposed an explanation of the photoelectric effect that used the idea of quantization:
