The difference between soft and hard $X-$rays is due to their:

In radiotherapy,$X$-rays are used to

In an $X$-ray tube,the wavelength of characteristic $X$-rays is a property of .......

When an $X$-ray of wavelength $0.5 \, \mathring{A}$ passes through a metal foil of thickness $3.5 \, mm$,its intensity is reduced to one-fourth of its initial value. The absorption coefficient of the metal is ..... $mm^{-1}$.

The wavelength of the series limit of the Lyman series in the hydrogen spectrum is $911 \ \mathring{A}$. Calculate the atomic number of the element that emits characteristic $X$-rays with a minimum wavelength of $0.7 \ \mathring{A}$.

The characteristic $X-$ray radiation is emitted,when