Chapter 29: Problem 44
Two sources produce electromagnetic waves. Source \(\mathrm{B}\) produces a wavelength that is three times the wavelength produced by source A. Each photon from source A has an energy of \(2.1 \times 10^{-18} \mathrm{J} .\) What is the energy of a photon from source \(\mathrm{B} ?\)
Short Answer
Expert verified
The energy of a photon from source B is \(0.7 \times 10^{-18} \text{ J}\."
Step by step solution
01
Understand the Relationship Between Wavelength and Energy
The energy of a photon is given by the formula: \( E = \frac{hc}{\lambda} \), where \( E \) is photon energy, \( h \) is Planck's constant \( (6.626 \times 10^{-34} \text{ m}^2 \text{ kg/s}) \), \( c \) is the speed of light \( (3 \times 10^8 \text{ m/s}) \), and \( \lambda \) is the wavelength.
02
Identify the Wavelengths of Sources A and B
Let \( \lambda_A \) be the wavelength of source A and \( \lambda_B \) be the wavelength of source B. It is given that \( \lambda_B = 3\lambda_A \).
03
Determine the Energy Equation for Source B
Given that the energy of a photon from source A is \( E_A = 2.1 \times 10^{-18} \text{ J} \), and \( E_A = \frac{hc}{\lambda_A} \), the energy of a photon from source B, \( E_B \), is \( E_B = \frac{hc}{3\lambda_A} \).
04
Relate the Energies of the Photons
Since \( E_B = \frac{hc}{3\lambda_A} \), we can write \( E_B = \frac{E_A}{3} \). This implies \( E_B = \frac{2.1 \times 10^{-18}}{3} \).
05
Calculate the Energy of a Photon from Source B
Compute \( E_B = \frac{2.1 \times 10^{-18}}{3} = 0.7 \times 10^{-18} \text{ J} \).
06
Verify the Solution
Each calculation is consistent with the relationship between wavelength and energy, confirming the energy of a photon from source B.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Wavelength
Wavelength is a fundamental concept when it comes to understanding electromagnetic waves. It refers to the distance between two consecutive peaks (or troughs) of a wave. It's commonly denoted by the Greek letter lambda (\( \lambda \)). In our exercise, the wavelength is crucial to determining the energy of photons from different sources.
- Wavelength is inversely proportional to energy: as wavelength increases, photon energy decreases.
- Unit of measurement for wavelength is meters (m).
Planck's constant
Planck's constant (\( h \)) is a fundamental constant in quantum mechanics, crucial for calculating photon energies. It represents the proportionality factor between the energy of a photon and the frequency of the electromagnetic wave.
- Value: \( 6.626 \times 10^{-34} \, \text{m}^2 \, \text{kg/s} \).
- Relates energy (E) to frequency (\( u \)): \( E = hu \).
Speed of Light
The speed of light (denoted as \( c \)) is a constant that represents the speed at which electromagnetic waves travel in a vacuum. Its value is approximately \( 3 \times 10^8 \, \text{m/s} \). This speed is not only incredibly fast, but it’s also essential for calculating photon energy.
- Key value in the equation \( E = \frac{hc}{\lambda} \).
- Makes the link between wavelength and the energy of a photon possible.
Electromagnetic Waves
Electromagnetic waves are waves propagated through the electromagnetic field, encompassing a broad spectrum that includes visible light, radio waves, X-rays, and more. They carry energy and travel through space.
- Comprised of oscillating electric and magnetic fields.
- Do not require a medium to travel; can move through a vacuum.