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( i ) X-rays are electromagnetic waves of wavelengths ranging from 0.1 A to 100 A and frequencies ranging from 10 16 Hz to 10 18 Hz .
( ii ) Soft X-rays have greater wavelength and lower frequency . ( iii ) Hard X-rays have lower wavelength and higher frequency . ( iv ) X-rays are produced by coolidge tube .
( v ) Molybdenum and tungsten provide suitable targets . These elements have large atomic number and high melting point for the purpose .
( vi ) The intensity of X – rays depends on the heating voltage or filament current .
( vii ) The kinetic energy of X-ray photons depends upon the voltage applied across the ends of coolidge tube .
( viii ) Energy of X-ray photon is given by E = hv = hc / λ
( ix ) If total energy of fast moving electron transfer to X-ray photon , then its energy , eV = hv = hc / λ
( x ) Wavelength of emitted X-rays is given by λ = hc / eV where , h = Planck ’ s constant , c = speed of light , e = electronic charge and V = potential difference applied across the ends of the tube .
( xi ) Absorption of X-rays
I = I o e - μx , where I o = initial intensity of X-rays , I = final intensity of emergent X-rays , x = thickness of material and μ = absorption coefficient .
Diffraction of X-rays
X-rays can be diffracted by crystals following Bragg ’ s law . According to which 2d sin θ = n λ
where , n = 1 , 2 , 3 , …, and d = spacing of crystal planes , θ = angle of diffraction .
X-rays Spectrum
The energy spectrum of X- . rays is a line spectrum , containing following series :
( i ) K – series When electrons of any higher orbit ( n = 2,3,4 , … ) jump to first orbit ( n = 1 ) then K-series of X-rays are produced .