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sam_p_r
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OK so you get to the matter wave equation 'lambda = h / p' using E=cp - which describes the energy for massless particles. I can understand this holding for when cp>>mc^2 , but not for when the mc^2 is comparible. Any help?
javierR said:Well the relations between energy/momentum and frequency/wavelength hold generally:
[tex]E=h\nu[/tex], [tex]p=h/\lambda[/tex]. It's the relation between E and p which is relevant in going from non-relativistic to relativistic to ultra-relativistic limits (as determined by the ratio [tex]pc/mc^{2}[/tex]). You could always use [tex]E^{2}=(pc)^{2}+(mc^{2})^{2}[/tex]. We ignore the second term in the ultra-relativistic limit, while in the non-relativistic limit, it simplifies to [tex]E=p^{2}/2m[/tex]. Otherwise, use the full expression.
sam_p_r said:OK so you get to the matter wave equation 'lambda = h / p' using E=cp - which describes the energy for massless particles. I can understand this holding for when cp>>mc^2 , but not for when the mc^2 is comparible. Any help?
alexepascual said:What specific problem do you see?.
javierR said:Well the relations between energy/momentum and frequency/wavelength hold generally:
[tex]E=h\nu[/tex], [tex]p=h/\lambda[/tex]. It's the relation between E and p which is relevant in going from non-relativistic to relativistic to ultra-relativistic limits (as determined by the ratio [tex]pc/mc^{2}[/tex]). You could always use [tex]E^{2}=(pc)^{2}+(mc^{2})^{2}[/tex]. We ignore the second term in the ultra-relativistic limit, while in the non-relativistic limit, it simplifies to [tex]E=p^{2}/2m[/tex]. Otherwise, use the full expression.
sam_p_r said:So what you're saying is that it only applies (in the exact lambda=h/p) for relativistic particles? (as its the only time where you can neglect mc^2).
Because in many examples in textbooks it applies the formula to non-relativistic conditions.
The De Broglie Wavelength is a concept in quantum mechanics that relates the wave-like properties of matter to its momentum and mass. It is named after physicist Louis de Broglie who proposed the idea in 1924.
The De Broglie Wavelength can be calculated using the equation λ = h/mv, where λ is the wavelength, h is Planck's constant, m is the mass of the object, and v is the velocity of the object. This equation shows that the wavelength is inversely proportional to the momentum of the object.
The De Broglie Wavelength is significant for slow objects because it shows that even objects with small momentum and relatively low energy have wave-like properties. This helps to explain phenomena such as diffraction and interference in particles.
The De Broglie Wavelength holds for slow objects because the wavelength is inversely proportional to the momentum, not the speed, of the object. This means that even slow-moving objects can have a relatively large De Broglie Wavelength if they have a small mass.
Some examples of slow objects with significant De Broglie Wavelength include electrons, which have a very small mass and thus a large De Broglie Wavelength, and atoms, which have a larger mass but can still exhibit wave-like behavior at low velocities.