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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.