Answer : 1. "0.1 nm"
Explanation :

X-rays have wavelengths from 0.01 to 10 nanometers, frequencies from 30 petahertz to 30 exahertz (3 × 1016 Hertz to 3 × 1019 hertz (Hz)) and energies from 120 electron volts to 120 kilo electron volts. The wavelength of X-rays is shorter than that of ultraviolet rays and longer than that of gamma rays.