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An electron and a proton have the same uncertainty in speed. Is the electron's uncertainty in momentum greater than, less than, or equal to the proton's uncertainty in momentum? Explain.

Short Answer

Expert verified
The uncertainty in an electron's momentum is less than that of a proton.

Step by step solution

01

Identifying the Variables

Let's identify the key variables: the electron and proton both have the same uncertainty in speed, which is represented as \( \Delta v_e = \Delta v_p \). The electron has a mass \( m_e \) and the proton has a mass \( m_p \).
02

Understanding Uncertainty in Momentum

The uncertainty principle involves momentum (\( p \)) and is given by \( \Delta p = m \cdot \Delta v \), where \( m \) is the mass and \( \Delta v \) is the uncertainty in speed.
03

Calculating Uncertainty in Momentum for the Electron

For the electron, we use its mass \( m_e \) and the shared uncertainty in speed \( \Delta v_e \) to find: \( \Delta p_e = m_e \cdot \Delta v_e \).
04

Calculating Uncertainty in Momentum for the Proton

For the proton, we use its mass \( m_p \) and the shared uncertainty in speed \( \Delta v_p \) to find: \( \Delta p_p = m_p \cdot \Delta v_p \).
05

Comparing the Uncertainties in Momentum

Since \( m_p > m_e \) and \( \Delta v_e = \Delta v_p \), it follows that \( \Delta p_p = m_p \cdot \Delta v_p > m_e \cdot \Delta v_e = \Delta p_e \). Thus, the uncertainty in momentum for the proton is greater than that for the electron.

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Key Concepts

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

Momentum
Momentum is a key concept in physics that helps us understand the movement of objects. It is defined as the product of an object's mass and its velocity. The formula for momentum (\( p \)) is given by:\[ p = m \, v \] where \( m \) is the mass and \( v \) is the velocity of the object. This basic definition explains why both the mass and speed of an object are critical in determining its momentum.
  • A heavier object with the same speed as a lighter one has more momentum.
  • Similarly, if two objects have the same mass, the faster one has more momentum.
In the scenario of uncertainty, the momentum also accounts for the possible variations in speed, termed as 'uncertainty in speed'. Thus, when we discuss the 'uncertainty in momentum', we're referring to the potential range of momentum due to changes in speed.
Electron
Electrons are tiny, subatomic particles that play a major role in chemistry and physics. They are negatively charged and orbit the nucleus of an atom. Despite their small size, electrons are pivotal in determining the chemical properties of atoms due to their charge and energy levels.
One fascinating aspect of electrons is their minuscule mass. Their mass is approximately \(9.109 \times 10^{-31} \text{ kg} \), making them much lighter than protons or neutrons.
  • Because of their small mass, any uncertainty in their velocity can result in a different level of uncertainty in momentum compared to heavier particles.
  • In high-precision physics experiments, this property of electrons plays a critical role.
Their light mass explains why, even with the same uncertainty in speed as protons, the electron's uncertainty in momentum will be less when compared with protons.
Proton
Protons are positively charged particles found within the nucleus of an atom. They, along with neutrons, give the nucleus its mass. The mass of a proton is significantly larger than that of an electron, about \(1.673 \times 10^{-27} \text{ kg}\).
  • This larger mass means that any changes in speed, or uncertainty in speed, will translate to a greater uncertainty in momentum.
  • Thus, compared to electrons, protons handle uncertainties in speed differently in terms of momentum.
The bigger mass of protons influences how we understand and measure them in scientific experiments.
Their role is crucial in maintaining atomic stability and contributing to the overall atomic structure.
Heisenberg Uncertainty
The Heisenberg Uncertainty Principle is a fundamental theory in quantum mechanics. It states that it is impossible to precisely measure both the position and momentum of a particle at the same time. The more accurately one is known, the less accurately the other can be known.The uncertainty principle is commonly expressed with the relation:\[ \Delta x \, \Delta p \geq \frac{\hbar}{2} \]where \( \Delta x \) and \( \Delta p \) represent the uncertainty in position and momentum, respectively, and \( \hbar \) is the reduced Planck's constant.
  • This principle is crucial in understanding behaviors at quantum scales like those of electrons.
  • It highlights why certain pairs of physical properties, like position and momentum, have inherent limits of precision.
In practical terms, Heisenberg's Uncertainty Principle underpins why uncertainties in speed lead to uncertainties in momentum, differing based on the particle's mass, as seen with electrons and protons.

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Most popular questions from this chapter

Light of frequency \(9.95 \times 10^{14} \mathrm{~Hz}\) ejects electrons from the surface of silver. If the maximum kinetic energy of the ejected electrons is \(0.180 \times 10^{-19} \mathrm{~J}\), what is the work function of silver?

Think \& Calculate A typical lightbulb contains a tungsten filament that reaches a temperature of about \(2850 \mathrm{~K}\), roughly half the surface temperature of the Sun. (a) Treating the filament as a blackbody, determine the frequency for which its radiation is a maximum. (b) Do you expect the lightbulb to radiate more energy in the visible or in the infrared part of the spectrum? Explain.

Think \& Calculate You have two different lightbulbs, as shown in Figure 24.23. One is a 150-W red bulb, and the other is a 25 -W blue bulb. (a) Which bulb emits more photons per second? (b) Which bulb emits photons of higher energy? (c) Calculate the number of photons emitted per second by each bulb. Take \(\lambda_{\text {red }}=650 \mathrm{~nm}\) and \(\lambda_{\text {blue }}=460 \mathrm{~nm}\). (Most of the electromagnetic radiation given off by incandescent lightbulbs is in the infrared portion of the spectrum. For the purposes of this problem, however, assume that all of the radiated power is at the wavelengths indicated.)

White light, with frequencies ranging from \(4.00 \times 10^{14} \mathrm{~Hz}\) to \(7.90 \times 10^{14} \mathrm{~Hz}\), is incident on a potassium surface. Given that the work function of potassium is \(2.24 \mathrm{eV}\), find (a) the maximum kinetic energy of electrons ejected from this surface and (b) the range of frequencies for which no electrons are ejected.

An electron and a helium atom are confined in separate boxes. The uncertainty in the electron's kinetic energy is the same as the uncertainty in the helium atom's kinetic energy. All other things being equal, is the box containing the electron larger, smaller, or the same size as the box containing the helium atom? Explain.

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