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An electron is in a one-dimensional box. When the electron is in its ground state, the longest-wavelength photon it can absorb is \(420 \mathrm{nm} .\) What is the next longest-wavelength photon it can absorb, again starting in the ground state?

Short Answer

Expert verified
The wavelength of the next longest-wavelength photon that the electron in its ground state can absorb, can be calculated with the aforementioned steps utilizing quantum mechanics concepts, the Planck-Einstein relation and the formula for energy levels in an infinite potential well.

Step by step solution

01

Convert the wavelength into energy

Use the Planck-Einstein relation to convert the initial wavelength (420 nm) into energy, which is \(E_1=h*c/\lambda_1\). Using \(h = 6.626*10^{-34} Js\) (Planck's constant) and \(c = 3.00*10^8 m/s\) (the speed of light), transform the wavelength (λ) from nanometers to meters before substituting the values in the equation.
02

Calculate the energy difference between first and second quantum states

The energy levels in an infinite potential well are given by \(E_n = n^2 * h^2 / 8mL^2\), where n is the quantum number, m is the mass of the electron, and L is the length of the well. The difference in energy when the electron jumps from the first to the second energy level is \(\Delta E = E_2 - E_1 = 3E_1 - E_1 = 2E_1\). This is the energy of the photon that must be absorbed for the electron to transition from the ground state (n=1) to the next level (n=2). The energy \(E_1\) was calculated in step 1.
03

Find the wavelength of the second photon

Now, find the wavelength of a photon with this new energy difference, using the rearranged Planck-Einstein relation, \(\lambda_2=h*c/\Delta E\), where \(\Delta E\) was calculated in step 2. This will give the new wavelength of the photon which the electron can absorb to jump from the ground state to the second energy level.

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Key Concepts

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

Infinite Potential Well
Imagine a tiny enclosure where particles like electrons can be found. This is what we refer to as an "infinite potential well". It is a simplified model used in quantum mechanics to help understand how electrons behave in confined spaces. Think of it like a box with infinitely high walls that an electron cannot escape from.

In this model, electrons can only exist in certain energy states. The energy levels are quantized, which means they can only take on specific values. This is due to the boundary conditions in the well—essentially, there are certain rules that the electron's wave function must follow. Unlike classical physics, where energy can vary smoothly, quantum mechanics dictates discrete energy levels.

The concept of an infinite potential well is crucial in understanding many quantum systems, including how electrons behave in atoms or semiconductors. By studying these models, we learn about how particles move and transition between different energy levels.
Energy Levels
Energy levels in a quantum system like an infinite potential well are akin to the steps on a staircase. Each step represents a possible energy state an electron can have. When an electron is "on" a certain energy level, it has a specific amount of energy and a corresponding wave pattern.

The energy levels are calculated using the formula: \[E_n = \frac{n^2 h^2}{8mL^2}\] Where:
  • \(E_n\) is the energy at the n-th level.
  • \(n\) is the quantum number (1, 2, 3,...).
  • \(h\) is Planck's constant.
  • \(m\) is the mass of the electron.
  • \(L\) is the length of the potential well.
The ground state, or the lowest energy level, is when \(n=1\). As \(n\) increases, so does the energy. When an electron jumps from one energy level to another, it absorbs or emits a photon corresponding to the energy difference between these levels.

Understanding energy levels is essential in predicting how electrons will behave in different situations, such as absorption of light or emission of radiation.
Planck-Einstein Relation
The link between the energy of a photon and its wavelength is elegantly given by the Planck-Einstein relation. This relation is foundational in understanding how light interacts with matter in quantum mechanics.

The Planck-Einstein relation is expressed as:\[E = \frac{hc}{\lambda}\] Where:
  • \(E\) is the energy of the photon.
  • \(h\) is Planck’s constant \((6.626 \times 10^{-34} \text{ Js})\).
  • \(c\) is the speed of light \((3.00 \times 10^8 \text{ m/s})\).
  • \(\lambda\) is the wavelength of the light.
By using this equation, you can calculate the energy of a photon when you know its wavelength, and vice versa.

This relationship is central to quantum mechanics and is used in a wide array of applications, from understanding the color of stars to the operation of lasers. It helps explain why electrons absorb specific wavelengths of light and how they transition between different energy states.

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Most popular questions from this chapter

Consider a particle in a box with rigid walls at \(x=0\) and \(x=L\). Let the particle be in the ground level. Calculate the probability \(|\psi|^{2} d x\) that the particle will be found in the interval \(x\) to \(x+d x\) for (a) \(x=L / 4 ;\) (b) \(x=L / 2 ;\) (c) \(x=3 L / 4\).

Dots that are the same size but made from different materials are compared. In the same transition, a dot of material 1 emits a photon of longer wavelength than the dot of material 2 does. Based on this model, what is a possible explanation? (a) The mass of the confined particle in material 1 is greater. (b) The mass of the confined particle in material 2 is greater. (c) The confined particles make more transitions per second in material 1 . (d) The confined particles make more transitions per second in material 2 .

A harmonic oscillator with mass \(m\) and force constant \(k^{\prime}\) is in an excited state that has quantum number \(n\). (a) Let \(p_{\max }=m v_{\max }\), where \(v_{\max }\) is the maximum speed calculated in the Newtonian analysis of the oscillator. Derive an expression for \(p_{\max }\) in terms of \(n, \hbar, k^{\prime},\) and \(m\). (b) Derive an expression for the classical amplitude \(A\) in terms of \(n, \hbar, k^{\prime},\) and \(m .\) (c) If \(\Delta x=A / \sqrt{2}\) and \(\Delta p_{x}=p_{\max } / \sqrt{2},\) what is the uncertainty product \(\Delta x \Delta p_{x} ?\) How does the uncertainty product depend on \(n ?\)

A particle with mass \(m\) is in a one-dimensional box with width \(L\). If the energy of the particle is \(9 \pi^{2} \hbar^{2} / 2 m L^{2},\) (a) what is the linear momentum of the particle and (b) what is the ratio of the width of the box to the de Broglie wavelength \(\lambda\) of the particle?

(a) Find the excitation energy from the ground level to the third excited level for an electron confined to a box of width \(0.360 \mathrm{nm}\). (b) The electron makes a transition from the \(n=1\) to \(n=4\) level by absorbing a photon. Calculate the wavelength of this photon.

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