Chapter 24: Problem 25
What's the shortest-wavelength \(x\) ray produced in a \(150-\mathrm{kV}\) x-ray tube? (a) \(8.3 \mathrm{nm} ;\) (b) \(0.83 \mathrm{nm} ;\) (c) \(0.083 \mathrm{nm}\); (d) \(8.3 \times 10^{-3} \mathrm{nm}\)
Short Answer
Expert verified
The shortest-wavelength x-ray is 0.083 nm, option (c).
Step by step solution
01
Identify the Formula
To find the shortest wavelength of x-rays produced, we use the formula \( \lambda = \frac{hc}{eV} \), where \( \lambda \) is the wavelength, \( h \) is Planck's constant \( 6.626 \times 10^{-34} \mathrm{m^2 \, kg/s} \), \( c \) is the speed of light \( 3 \times 10^8 \, \mathrm{m/s} \), \( e \) is the charge of an electron \( 1.6 \times 10^{-19} \, \mathrm{C} \), and \( V \) is the accelerating voltage in the x-ray tube.
02
Convert Units
Given voltage \( V = 150 \mathrm{kV} \), convert this to volts: \( 150 \mathrm{kV} = 150,000 \, \mathrm{V} \). This is necessary to ensure all units are compatible.
03
Substitute Values
Substitute the known values into the formula: \[ \lambda = \frac{6.626 \times 10^{-34} \times 3 \times 10^8}{1.6 \times 10^{-19} \times 150,000} \] Calculate the result.
04
Calculate Wavelength
Evaluate the expression: \[ \lambda = \frac{6.626 \times 3}{1.6 \times 150} \times 10^{-11} \]\[ \lambda = \frac{19.878}{240} \times 10^{-11} \] \[ \lambda = 0.082825 \times 10^{-9} \mathrm{m} \] Convert to nanometers: \( \lambda = 0.082825 \, \mathrm{nm} \approx 0.083 \, \mathrm{nm} \).
05
Select the Correct Option
Compare the calculated wavelength \( 0.083 \, \mathrm{nm} \) with the given options. The correct answer is option (c) \( 0.083 \, \mathrm{nm} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Wavelength Calculation
When calculating the wavelength of X-rays produced in an X-ray tube, it is essential to use the formula \( \lambda = \frac{hc}{eV} \). This formula helps to determine the shortest wavelength possible based on the voltage given. Here's a breakdown:
- \( \lambda \) represents the wavelength and is typically expressed in meters or nanometers.
- \( h \) is Planck’s constant, a fundamental constant that describes the smallest possible quantum of energy.
- \( c \) is the speed of light in a vacuum, another key constant in physics.
- \( e \) is the electron charge, indicating how an electron interacts with electric and magnetic fields.
- \( V \) is the voltage applied across the X-ray tube, crucial in determining the energy of electrons which impacts the wavelength of emitted X-rays.
Planck's Constant
Planck's constant (\( h \)) is one of the fundamental constants in physics, essential for understanding quantum mechanics. It is valued at \( 6.626 \times 10^{-34} \) joule-seconds. This constant relates the energy of photons to their frequency with the formula \( E = hf \), where \( E \) is energy, \( h \) is Planck’s constant, and \( f \) is frequency.
In the context of X-ray wavelength calculations, Planck's constant allows us to relate the energy of the electrons caused by the X-ray tube's voltage to the electromagnetic radiation emitted. This is key in the formula \( \lambda = \frac{hc}{eV} \), as it helps determine the energy transformed into the emitted wavelength.
In the context of X-ray wavelength calculations, Planck's constant allows us to relate the energy of the electrons caused by the X-ray tube's voltage to the electromagnetic radiation emitted. This is key in the formula \( \lambda = \frac{hc}{eV} \), as it helps determine the energy transformed into the emitted wavelength.
Speed of Light
The speed of light (\( c \)) is a critical constant in physics, symbolized as \( 3 \times 10^8 \) meters per second. This value represents how fast light travels through a vacuum. It is a fundamental element in various equations in physics, reflecting how energy and matter interact at the smallest scales.
In the calculation of X-ray wavelengths, the speed of light comes into play within the formula \( \lambda = \frac{hc}{eV} \). It helps to define the relationship between the energy of particles accelerated by the X-ray tube and the electromagnetic radiation emitted. Knowing the speed of light aids in transforming energy calculations into wavelength values.
In the calculation of X-ray wavelengths, the speed of light comes into play within the formula \( \lambda = \frac{hc}{eV} \). It helps to define the relationship between the energy of particles accelerated by the X-ray tube and the electromagnetic radiation emitted. Knowing the speed of light aids in transforming energy calculations into wavelength values.
Electron Charge
The electron charge (\( e \)) is a fundamental property of electrons, which dictates how these particles interact with electromagnetic fields. The standard value is \( 1.6 \times 10^{-19} \) coulombs. This charge determines the force and acceleration an electron experiences in an electric field.
In the equation \( \lambda = \frac{hc}{eV} \), the electron charge is used to convert the kinetic energy of the accelerated electrons into the energy emitted as X-ray photons. It reflects the basic charge property necessary for calculating the energy delivered by the electron as it moves through an electric potential (voltage \( V \)) in the X-ray tube. Understanding the electron charge is crucial in precisely calculating the energy-to-wavelength conversion in physics.
In the equation \( \lambda = \frac{hc}{eV} \), the electron charge is used to convert the kinetic energy of the accelerated electrons into the energy emitted as X-ray photons. It reflects the basic charge property necessary for calculating the energy delivered by the electron as it moves through an electric potential (voltage \( V \)) in the X-ray tube. Understanding the electron charge is crucial in precisely calculating the energy-to-wavelength conversion in physics.