JEE Advanced Model Paper 16 with solutions for online practice

A target element A is bombarded with electrons and the wavelengths of thecharacteristic spectrum are measured. A second characteristic spectrum is alsoobtained, because of an impurity in the target. The wavelength of the Ka lines are 196pm (element A) and 169 pm (impurity). If the atomic number of impurity is z = (10x - 1) . Find the value of x. (atomic number of element A is 27).