The intensity of X-rays from a Coolidge tube is plotted against wavelength as shown in the figure. The minimum wavelength found is λc and the wavelength of the Kα line is λK. As the accelerating voltage is increased

Wavelength λK. is independent of the accelerating voltage (V) while the minimum wavelength )λc is inversely proportional to V. Therefore as V increases λK remains unchanged whereas λc decreases or λK- λcwill increase.