Chapter 12: Problem 1
What is the short-wavelength limit of the continuum produced by an X-ray tube having a tungsten target and operated at \(50 \mathrm{kV} ?\)
Short Answer
Expert verified
The short-wavelength limit is approximately 0.0248 nm.
Step by step solution
01
Understand the Problem
We need to determine the short-wavelength limit of the X-ray continuum spectrum for an X-ray tube with a tungsten target operated at a potential difference of 50 kV.
02
Use the Formula for Short Wavelength Limit
The short-wavelength limit (\( \lambda_{min} \)) is found using the equation:\[\lambda_{min} = \frac{hc}{eV}\]where \( h \) is Planck's constant (\( 6.626 \times 10^{-34} \; \text{Js} \)), \( c \) is the speed of light in a vacuum (\( 3.00 \times 10^{8} \; \text{m/s} \)), \( e \) is the elementary charge (\( 1.602 \times 10^{-19} \; \text{C} \)), and \( V \) is the accelerating voltage (50 kV or 50,000 V).
03
Plug in the Values
Substitute the given values into the formula:\[\lambda_{min} = \frac{6.626 \times 10^{-34} \times 3.00 \times 10^{8}}{1.602 \times 10^{-19} \times 50,000}\]
04
Calculate the Result
Perform the calculation:\[\lambda_{min} = \frac{1.9878 \times 10^{-25}}{8.01 \times 10^{-15}} \approx 2.48 \times 10^{-11} \; \text{m}\]
05
Convert to Nanometers
Since X-ray wavelengths are often expressed in nanometers, convert the result:\[\lambda_{min} = 2.48 \times 10^{-11} \; \text{m} = 0.0248 \; \text{nm}\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
X-ray tube
An X-ray tube is essential equipment used in various applications like medical imaging and material analysis. It operates by generating X-rays through a process that involves accelerating electrons towards a target material. When these high-speed electrons strike the target, X-rays are produced.
The basic components of an X-ray tube include:
The basic components of an X-ray tube include:
- A cathode, which emits electrons when heated.
- An anode, typically made of a metal such as tungsten, where the electrons collide.
- A vacuum tube, which ensures that electrons travel from the cathode to the anode without interference from air molecules.
tungsten target
In an X-ray tube, the target material is crucial as it significantly influences the properties of the generated X-rays. Tungsten is commonly used for this purpose due to several advantageous properties.
Key reasons for using tungsten as a target material include:
Key reasons for using tungsten as a target material include:
- High atomic number: Tungsten, with its high atomic number, is efficient at producing X-rays because it can decelerate the fast-moving electrons more effectively, leading to the emission of higher energy radiation.
- High melting point: As the electron collision generates significant heat, tungsten's high melting point (around 3422°C) makes it ideal for withstanding the thermal stress in an X-ray tube.
- Good thermal conductivity: It helps to dissipate the heat quickly to avoid damage to the target.
accelerating voltage
Accelerating voltage in an X-ray tube plays a critical role in determining the energy and wavelength of the produced X-rays. It refers to the potential difference applied between the cathode and anode.
When a high voltage is applied:
When a high voltage is applied:
- The electrons emitted from the cathode accelerate towards the anode.
- The speed of the electrons increases with higher voltages, resulting in more energetic collisions with the target.
- These collisions produce higher energy X-rays, capable of shorter wavelengths.
continuum spectrum
The continuum spectrum, in the context of X-ray production, refers to the broad range of X-ray wavelengths that can be generated by an X-ray tube. This spectrum arises because the energy of the electrons, and consequently the energy of the emitted X-rays, varies due to the random processes involved in electron deceleration when they strike the target.
Characteristics of the X-ray continuum spectrum include:
Characteristics of the X-ray continuum spectrum include:
- A broad wavelength range: The X-ray tube produces X-rays across a wide spectrum rather than a single, distinct wavelength.
- Short-wavelength limit: This represents the smallest wavelength within the spectrum, determined by the maximum energy of the electrons, which depends on the accelerating voltage.
- Dependence on target and voltage: The specifics of the continuum spectrum are influenced by the target material and the voltage applied, affecting both the intensity and the wavelength range of the X-rays.