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Questions and Answers
What is the range of wavelength of X-rays?
What determines the amount of energy carried by each photon of X-rays?
What is the purpose of the high positive potential in an X-ray tube?
What is the ratio of energy converted to X-ray photons to energy converted to heat in an X-ray tube?
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What is the purpose of the evacuated space in an X-ray tube?
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What is the relationship between the atomic number of the anode and the intensity of the X-ray beam?
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What is the unit of Planck's constant?
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What is the product of the tube current and time that controls the number of electrons produced in an X-ray tube?
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What is the primary reason for using a high atomic number material as the anode in an X-ray tube?
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What is the main function of the filament in an X-ray tube?
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Why is the evacuated space in an X-ray tube necessary?
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What is the purpose of using two filaments in an X-ray tube?
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What is the most significant challenge in the design of an X-ray tube?
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What is the relationship between the energy of the electrons and the energy of the X-ray photons in an X-ray tube?
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Why is tungsten used as the anode material in an X-ray tube?
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What is the primary advantage of using a small focal spot in an X-ray tube?
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What is the formula that relates the energy of the X-ray photons to the frequency of the radiation?
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What is the primary application of X-rays?
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Study Notes
X-Rays
- Electromagnetic radiation with very short wavelength (1-0.1 Å) and high penetrating power.
- Useful in diagnosis and radiotherapy.
Energy of X-Rays
- Energy of each photon depends on the frequency of radiation.
- Energy (E) = hυ = hc / λ, where h = Planck's constant (6.6 × 10⁻³⁴ J·s), c = velocity of light (3 × 10⁸ m/s), and υ = frequency of radiation.
X-Ray Production
- Produced when highly energetic electrons interact with matter, converting kinetic energy into electromagnetic radiation.
- Main components of an X-ray tube:
- Source of electrons (cathode, filament), controlling the number of electrons and X-ray photons through tube current and time (mAs).
- Evacuated space (glass envelope) for accelerating electrons.
- High positive potential (kV) to control electron energy and X-ray photon energy.
- Target (anode) for electrons to strike.
X-Ray Tube Efficiency
- Up to 99% of accelerated electron energy is converted to heat, while approximately 1% is converted to X-ray photons.
- Anode atomic number (Z) affects X-ray beam intensity, with higher Z (e.g., tungsten, Z = 74) producing more intense beams.
X-Rays
- X-rays are electromagnetic radiation (EMR) with a very short wavelength (λ 1-0.1 A°) and high penetrating power.
- They are useful in diagnosis and radiotherapy.
Energy of X-Rays
- The energy carried by each photon depends on the frequency of radiation: E = h υ = h c / λ.
- h is Planck's constant = 6.610−34 (joule.sec) and c is the velocity of light = 310^8 m/sec.
X-Ray Production
- X-rays are produced when highly energetic electrons interact with matter, converting kinetic energy into electromagnetic radiation.
- The main components of the X-ray tube are:
- A source of electrons (cathode, filament)
- An evacuated space to accelerate electrons
- A high positive potential to control electron energy
- A target for electrons to strike (anode)
X-Ray Tube Characteristics
- In the X-ray tube, up to 99% of accelerated electrons' energy is converted to heat, and approximately 1% is converted to X-ray photons.
- The higher the atomic number (Z) of the anode, the more intense the X-ray beam produced.
- Techniques to overcome overheating in the anode:
- Use an anode material with a high melting point (e.g., tungsten at 3400 C°)
- Equip the X-ray tube with two filaments for interchangeable focal spot sizes
- Increase the area struck by electrons (focal spot area) without increasing image blurring by angulating the anode (line-focus principle)
- Use a rotating anode X-ray tube (3600 rotations per minute)
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Description
Learn about X-rays, a type of electromagnetic radiation with high penetrating power, used in diagnosis and radiotherapy. Study the relationship between energy, frequency, and wavelength of X-rays.
