How do I calculate the wavelengths of electromagnetic radiation?

In 1895 the physicist Wilhelm Conrad Röntgen discovered a new kind of radiation, which he called X-rays. The rays were generated when high energy electrons were suddenly stopped by striking a metal target inside a vacuum tube – the X-ray tube. It was subsequently shown that X-rays are an electromagnetic radiation, just like light, heat and radiowaves.

Wavelengths of electromagnetic radiation

The wavelength lambda (λ) of electromagnetic radiation is expressed in m, cm, mm, micrometer (μm), nanometer (nm) and Ångstrom (1 Å = 0.1 nm).

What is an X-ray tube?