Problem 5.220

How many times will the intensity of a narrow X-ray beam of wavelength 20 pm decrease after passing through a lead plate of thickness \(d=1.0 \mathrm{~mm}\) if the mass absorption coefficient for the given radiation wavelength is equal to \(\mu / \rho=3.6 \mathrm{~cm}^{2} / \mathrm{g}\) ?