A venetian blind is essentially a diffraction gratingnot for visible light, but for waves with much longer

Question:

A venetian blind is essentially a diffraction grating—not for visible light, but for waves with much longer wave-lengths. If the spacing between the slats of a blind is 2.5 cm,
(a) For what wavelength would there be a first-order maximum at an angle of 10o, and
(b) What type of radiation is this?