Figure shows the intensity-wavelength relations of X-rays coming from two different Coolidge tubes. The solid curve represents the relation for the tube A in which the potential difference between the target and the filament is V_A and the atomic number of the target material is Z_A. These quantities are V_B and Z_B for the other tube. Then,

Question

Philoid · Accepted Answer

The cut-off frequency is given by:

where, λ_min is the cut-off wavelength, h is the Planck’s constant (6.62607004 × 10^-34 m² kg / s), c is the speed of light in vacuum, e is the charge of the electron and V is the potential difference applied at the ends of the tube
So, greater the operating voltage, lesser would be the cut-off wavelength. As, λ_min is less of A than B, V_A > V_B .
From Moseley’s law, √v = a (Z – b), therefore in terms of wavelength(λ ), we have
where, “a” represents the proportionality constant while “b” represents the screening constant and Z is the atomic number of the element.
Looking at the characteristic peaks, we can see that λ _A >λ_B . So from the inverse relation, Z_AB .