X-Rays Notes

 X-Rays 

X-rays

• When fast-moving electrons strike a heavy target (having high mass no., high melting & boiling points) after rescattering through the target, an electromagnetic wave of a short wavelength of about 10-10 m is produced, they are naming as X-rays. 

• X-rays are discovered by Roentzen. 

• X-rays are called Roentzen rays. 

 • All X-rays are not of a single wavelength. 

• Different X-rays have different wavelengths but lines within the range. 

Properties of X-rays • X-rays are electromagnetic waves. • X-rays are not deflected by fields (electric & magnetic). • They move along the straight path with a velocity of light in a vacuum. • X-rays can cause a photo-electric effect. • X-rays undergoes reflection, refraction, diffraction, interference & polarization. • They produce illumination of fluorescent materials on which they fall. • They ionize the gas through which they pass. • They can penetrate thin materials like wood, thin sheet, etc. • They do not pass through heavy metals and bones. • X-rays cast their shadow on the screen. • They affect photographic plates. • X-rays fall on metal surfaces having high mass no. secondary X-rays are produced.

Production

• Filament: Tungsten, it has a low work function. • Target: Molybdenum target is more suitable (Coolidge tube method) which has a high mass no., high melting point, high boiling points, etc. • X-rays production is the inverse phenomenon of the photo-electric effect. • In the time of X-ray production, the majority percentage of the incident power is converted into heat. • Minority percentage of the incident power is converted into X-ray radiations.

• Soft X-rays: - having a long wavelength - low energetic and low penetrating power

• Hard X-rays: - having short wavelength more energetic, having high penetrating power

• There is the circulation of cold water around the target to maintain heat (temperature). • The ionization power of X-rays depends on filament current whereas the penetrating power of X-rays depends on high p.d. provided by H.T.B. in between filament and target. • Intensity of X-rays is proportional to the number of electrons emitted per second. • Quality of X-rays implies the penetrating power of X-rays which is controlled by varying the potential difference.

Intensity of X-rays

Diffraction of X-rays

• Von Lane verified the wave nature of X-rays. • Von Lane verified X-ray diffraction by using atomic crystal as a diffraction grating. Von Lane experiment for X-rays diffraction

• The major role played by Zns crystal for diffraction of X-rays. • The bending of X-rays around the corner of an obstacle is known as X-ray diffraction. • The formation of dark & faint spots, is due to unequal energy distribution during X-ray diffraction through ZnS crystal. • Diffraction of X-rays verifies its wave nature.

X-ray spectra

X-rays are produced from X-rays tube and they carry different wavelengths. At a specified accelerating potential, the intensity of X-rays depends upon their wavelength. The graph between the intensity of X-rays & wavelength of X-rays at specified accelerating potential is called X-rays spectra.

X-rays Doze • Doze of X-rays is measured in terms of produced ions or free energy through ionization. • Doze measured in Roentgen. • Roentgen measures ionization power. • Safe doze for human beings per week is one Roentgen.

Uses of X-rays 1. Highly used in medical fields such as surgery, therapy, cancer treatment, tumor treatment, etc. 2. Highly used in the engineering field. 3. Used in the industrial field. 4. Used in the detective field. 5. Used in space exploration. 6. Used in the scientific research field.