Answer:
An electromagnetic wave with a wavelength of 4 x 10^-11 meters is in the X-ray band of the electromagnetic spectrum.
The electromagnetic spectrum is the range of all types of electromagnetic radiation, arranged according to wavelength or frequency. The different bands of the electromagnetic spectrum include:
radio waves
microwaves
infrared
visible light
ultraviolet
X-rays
gamma rays
X-rays have a wavelength range of around 10^-11 to 10^-8 meters. Therefore, the wavelength of 4 x 10^-11 meters falls within this range and is classified as an X-ray.