6PHOTONS-The energy of a light-wave is carried by packets called photons-The energy of a photon depends on the light’s wavelength-Smaller wavelengths have larger energies
7Photon energies are usually given in units of electron volts (eV) ENERGYPhoton energies are usually given in units of electron volts (eV)1 eV = 1.602x10-19 JoulesNeed 56,000,000,000, 000,000,000,000 eV tocook an egg.
11X-Ray Tube X-ray tube consists of the following major parts 1- Filament: made from tungsten wire which is heated electrically at a potential difference of 8 to 12 V to a high temperature so that electrons ‘boiled off’ from its surface. These electrons form the tube beam.The filament is located within a negatively charged nickel cathode which is shaped so that a precise beam geometry is obtained.
12X-Ray Tube2- Cathode: this houses the filament and is manufactured from nickel . The filament is located within a cup having sharp contoured edges which electrostatically focus the electron beam. The cathode cup is independently supplied with a high negative voltage 3- Anode: is manufacture from tungsten (high melting metal). Dental units and small mobile X-ray units use stationary or fixed anode design. The most efficient design however uses a rotating-disk anode which enables higher X-ray output owing to more effective cooling.