Thursday, July 7, 2011

X-ray: Yu Chong, Davina, Jia Le, Jun Hong




What is X-ray?

- A form of electromagnetic radiation.

  • Wavelength: 0.01-10 nanometers
  • Frequency: 3×1016 Hz to 3×1019 Hz
  • Energy: 120 eV to 120 keV.
  • Soft X-ray: about 0.12 to 12 keV

(10 to 0.10 nm wavelength)

  • Hard X-ray: about 12 to 120 keV

(0.10 to 0.01 nm wavelength)

What is some usages of it?

Another use of radiography is in the examination and analysis of paintings, where studies can reveal such details as the age of a painting and underlying brushstroke techniques that help to identify or verify the artist. X rays are used in several techniques that can provide enlarged images of the structure of opaque objects. These techniques, collectively referred to as X-ray microscopy or microradiography, can also be used in the quantitative analysis of many materials. It is also used in X-ray therapy to destroy diseased cells.

What is one danger of it?

  • Can cause mutations
  • One of the dangers in the use of X rays is that they can destroy living tissue and can cause severe skin burns on human flesh exposed for too long a time.

How many times can someone be exposed to X-ray?

  • Less than 36 times per year

- The radiation is equivalent to over 10 days of normal light radiation

Safety of doctors and attendants in the hospital

Depending on the peak voltage, the thickness of lead that is needed to be worn differs

Created by

  1. X-ray fluorescence: If the electron has enough energy it can knock an orbital electron out of the inner electron shell of a metal atom, and as a result electrons from higher energy levels then fill up the vacancy and X-ray photons are emitted. This process produces an emission spectrum of X-rays at a few discrete frequencies, sometimes referred to as the spectral lines. The spectral lines generated depend on the target (anode) element used and thus are called characteristic lines. Usually these are transitions from upper shells into K shell (called K lines), into L shell (called L lines) and so on.
  2. Bremsstrahlung: This is radiation given off by the electrons as they are scattered by the strong electric field near the high-Z (proton-number) nuclei. These X-rays have a continuous spectrum. The intensity of the X-rays increases linearly with decreasing frequency, from zero at the energy of th e incident electrons, the voltage on the X-ray tube.

What is the instrument used to create X-ray?

X-rays can be generated by an X-ray tube, a vacuum tube that uses a high voltage to accelerate the electrons released by a hot cathode to a high velocity. The high velocity electrons collide with a metal target, the anode, creating the X-rays. In medical X-ray tubes the target is usually tungsten or a more crack-resistant alloy of rhenium (5%) and tungsten (95%), but sometimes molybdenum for more specialized applications, such as when soft X-rays are needed as in mammography. In crystallography, a copper target is most common, with cobalt often being used when fluorescence from iron content in the sample might otherwise present a problem.

1 comment:

  1. Organized information into a table format, excellent work!