X-RAY  WAVE  LENGTH

A.U.  Angstrom,  angstrom unit

            1 10 billionth of a meter (10^-10 meter)

            1 10 millionth of a millimeter (10^-7 millimeter)

            1/10 nanometer (nm)

            10 angstroms = 1 nanometer

nm     nanometer

            10 times greater than an angstrom

            1 billionth of a meter (10^-9 meter)

            1 millionth of a millimeter (10^-6 millimeter)

            1 thousandth of a micron (10^-3 micron)

            nanometer is also called a millimicron, abbreviated mµ

         (Not to be confused with a micrometer, abbreviated µm, which is 1 millionth of a meter (10^-6 meter);  therefore, 1  µm = 1000  millimicrons [1000 nanometers].)

X-ray wavelength = less than 5 A.U. 

The very longest x-ray wavelengths (“soft” x-rays) would be ½ a nanometer

Typical diagnostic x-ray wavelengths would be in the range of 1/10^th to 1/100^th of a nanometer (1 to 1/10^th A.U.)

Industrial x-ray and therapeutic radiation therapy wavelengths may be down to 100,000^th of a nanometer.

For comparison, visible light is in the range of 3900 to 7700 A.U. (angstroms).

Infrared is longer, in the range of 7500 to 10 million angstroms (0.75 to 1000 µm)

So if you took a millimeter and divided it into a million parts, and then took less than a 1/10^th of that, you would have the average wavelength of x-ray. 

This is why x-ray passes through us.  It literally fits through the spaces in our atoms.

In contrast, a longer wavelength such as visible light is not able to pass through us.  We thus create a shadow when we block the light.  Wavelengths of visible light are roughly 4000 to 8000 times longer than an average wavelength of x-ray.