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What is the de Broglie wavelength for an electron with speed (a) \(v=0.480 c\) and \((b) v=0.960 c ?\) (Hint: Use the correct relativistic expression for linear momentum if necessary.)

Short Answer

Expert verified
The de Broglie wavelengths for an electron traveling at \(v = 0.480c\) and \(v = 0.960c\) can be found by simply understanding the de Broglie equation and the relativistic definition of momentum, then substituting the corresponding values into the equation and performing the division.

Step by step solution

01

Understanding de Broglie's Equation

The de Broglie equation is a basic equation in quantum physics and it relates the wavelength of a wave (\(\lambda\)) with its associated particle's momentum (\(p\)). The equation is \(\lambda = h / p\), where \(h\) is Planck's constant (\(6.62607015 \times 10^{-34} \, m^2 kg / s\))
02

Finding Momentum for \(v = 0.480c\)

If \(v < 0.1c\), Newtonian physics can be used. However for \(v = 0.480c\), it's necessary to use relativistic definitions. The relativistic momentum equation is \(p = \gamma m v\), where \(m\) is electron's mass (\(9.11 \times 10^{-31}\,kg\)), and \(\gamma\) is the Lorentz factor. The Lorentz factor can be calculated as \(\gamma = 1 / \sqrt{1 - (v/c)^2}\).
03

Calculate the Wavelength for \(v = 0.480c\)

Having the momentum, we can simply substitute \(p\) into de Broglie's equation to find out the associated wavelength.
04

Finding Momentum for \(v = 0.960c\)

We follow the same procedure to calculate the relativistic momentum for the electron when \(v = 0.960c\).
05

Calculate the Wavelength for \(v = 0.960c\)

Again, substitute \(p\) in de Broglie's equation to find the associated wavelength.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Relativistic Momentum
When particles travel at high speeds, close to the speed of light (\(c\)), we can't use the regular formula for momentum due to the effects of relativity. Traditional momentum is calculated as \(p = mv\), where \(m\) is mass and \(v\) is velocity. However, at speeds close to the speed of light, we must account for relativistic effects using the formula: \(p = \gamma m v\).
Relativistic momentum is crucial when dealing with particles moving at a significant fraction of light speed, such as electrons in this problem. The reason is their mass effectively increases due to relativistic effects.
The "\(\gamma\)" in the equation stands for the Lorentz factor, which plays a pivotal role in ensuring the momentum accounts for these high-speed tweaks. By using this adjusted momentum, physicists can accurately predict behaviors and interactions at tiny scales and high velocities.
Planck's Constant
Planck's constant is fundamental in linking the world of the tiny particles to wave phenomena. Represented by \(h\), its value is approximately \(6.626 \times 10^{-34} \, \text{m}^2 \text{kg/s}\). This constant appears in the de Broglie equation \(\lambda = h/p\), connecting wave properties with particle momentum.
  • It's a bridge between classical physics and quantum mechanics.
  • Quantifies the action required to shift the energy level for particles such as photons and electrons.
In this exercise, Planck’s constant helps us find the wavelength of electrons moving at relativistic speeds. By dividing Planck’s constant by the momentum calculated using the relativistic formula, we can determine the de Broglie wavelength, revealing crucial insights into wave-particle dual nature.
Lorentz Factor
The Lorentz factor, symbolized by \(\gamma\), modifies calculations of time, length, and other physical quantities for particles moving close to the speed of light. It's calculated as \(\gamma = 1 / \sqrt{1 - (v/c)^2}\), where \(v\) is velocity and \(c\) is speed of light.
In the realm of special relativity:
  • The Lorentz factor quantifies how much relativistic effects alter physical parameters.
  • For example, it shows how time dilation and length contraction happen as \(v\) approaches \(c\).
In this problem, \(\gamma\) ensures the momentum values are accurate at high velocities. For velocities such as \(0.480c\) and \(0.960c\), using the Lorentz factor helps account for the difference between everyday Newtonian expectations and what really happens at near-light speeds.

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Most popular questions from this chapter

(a) A nonrelativistic free particle with mass \(m\) has kinetic energy \(K\). Derive an expression for the de Broglie wavelength of the particle in terms of \(m\) and \(K\). (b) What is the de Broglie wavelength of an \(800 \mathrm{eV}\) electron?

(a) What accelerating potential is needed to produce electrons of wavelength \(5.00 \mathrm{nm} ?\) (b) What would be the energy of photons having the same wavelength as these electrons? (c) What would be the wavelength of photons having the same energy as the electrons in part (a)?

CP A beam of electrons is accelerated from rest and then passes through a pair of identical thin slits that are \(1.25 \mathrm{nm}\) apart. You observe that the first double-slit interference dark fringe occurs at \(\pm 18.0^{\circ}\) from the original direction of the beam when viewed on a distant screen. (a) Are these electrons relativistic? How do you know? (b) Through what potential difference were the electrons accelerated?

Doorway Diffraction. If your wavelength were \(1.0 \mathrm{~m},\) you would undergo considerable diffraction in moving through a doorway. (a) What must your speed be for you to have this wavelength? (Assume that your mass is \(60.0 \mathrm{~kg} .\) ) (b) At the speed calculated in part (a), how many years would it take you to move \(0.80 \mathrm{~m}\) (one step)? Will you notice diffraction effects as you walk through doorways?

Find the longest and shortest wavelengths in the Lyman and Paschen series for hydrogen. In what region of the electromagnetic spectrum does each series lie?

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