Infra red spectrum and molecule to show IR spectrum:

Infrared region of the electromagnetic spectrum divided into the following three regions

• Near IR,
• Mid IR and
• Far IR

It is the mid-IR region that is most commonly used.

The prerequisite for a molecule to show IR spectrum is that the vibrations within it must cause a net change in the dipole moment of the molecule.  YES, the asymmetric stretching mode of H₂O molecule will be IR active.