We are given the wavelength of an electromagnetic wave which is 6.11×10-5 m.
We are asked to determine its frequency.
Recall that the relationship between wavelength and frequency is given by

Where λ is the wavelength, f is the frequency, and v is the speed of light.
The speed of light is 3.00×10^8 m/s

Therefore, the frequency of the wave is 4.91×10^12 Hz.
We are also asked in which region of the electromagnetic spectrum is this radiation.
The above frequency range (4.91×10^12 Hz) is in the infrared region of the electromagnetic spectrum.
Therefore, option a.) Infrared is the correct answer.