Reflection/Absorption in Drude Metals

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In summary, the Drude model of metals predicts that metals cannot sustain an electromagnetic wave for frequencies lower than the plasma frequency, resulting in a perfectly reflected incoming wave due to the imaginary wavevector. However, absorption may occur in the immediate vicinity of the plasma frequency. In real life, absorption can reduce the reflectivity of metals, such as copper or gold, where interband transitions occur below the plasma frequency.
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nmbr28albert
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One result of the Drude model of metals is that metals cannot sustain an electromagnetic wave for frequencies lower than the plasma frequency - since the wavevector is imaginary the wave will be evanescent and won't propagate. The books I've read say however, that this means the metal will perfectly reflect an incoming wave. None of the books mention absorption of the radiation at this point however. Is absorption not a consideration because there is an evanescent wave then? In real life there should always be some absorption happening though, so how would we reconcile the reflection/absorption processes?
 
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In the Drude model, absorption only happens in the immediate vicinity of the plasma frequency.
In real life metals, absorption will reduce the reflectivity of the metal, as is the case e.g. in copper or gold where interband transitions from the d-band to the conduction band are present below the plasma frequency.
 
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1. What is the Drude model and how does it explain reflection and absorption in metals?

The Drude model is a classical theory that describes the behavior of electrons in a metal. It proposes that free electrons in a metal are constantly colliding with each other and with the ions in the metal lattice, resulting in a net drift motion. This model explains the reflection and absorption of light in metals by considering the interaction between incident light and the free electrons in the metal.

2. How does the Drude model account for the reflectivity of metals?

The Drude model explains reflectivity by considering the free electrons in the metal as a collective oscillating system. When light is incident on a metal, it interacts with the free electrons and induces oscillations, which then re-radiate the incident light in all directions. This results in high reflectivity of metals, as the majority of incident light is reflected rather than absorbed.

3. How is the absorption of light in metals related to the Drude model?

The Drude model explains absorption in metals as the result of collisions between free electrons and the ions in the metal lattice. These collisions cause the free electrons to lose energy, resulting in the absorption of the incident light. The absorption in metals is also affected by the frequency of the incident light, with higher frequencies resulting in greater absorption.

4. Can the Drude model be applied to all metals?

No, the Drude model is most accurate for metals with high electron densities such as copper, silver, and gold. It does not accurately describe the behavior of electrons in metals with low electron densities, such as aluminum and magnesium. In these cases, the Drude model needs to be modified to account for the band structure of the metal.

5. How does temperature affect the reflectivity and absorption of metals according to the Drude model?

According to the Drude model, as the temperature of a metal increases, the average kinetic energy of the free electrons also increases. This results in a decrease in reflectivity and an increase in absorption, as the higher energy electrons are more likely to collide with the metal ions and lose energy. This is why most metals have higher reflectivity and lower absorption at lower temperatures.

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