Iron filings do not align to radiated electromagnetic waves. Iron filings align with stationary or slowly changing magnetic fields, not with rapidly changing electromagnetic waves.
When a magnetic field is applied to a region where iron filings are present, the filings align themselves along the lines of magnetic force. This alignment occurs due to the magnetic properties of iron, specifically its ability to become magnetized in the presence of a magnetic field.
However, electromagnetic waves consist of rapidly changing electric and magnetic fields that oscillate in both magnitude and direction as they propagate through space. The timescale of these changes is typically in the range of nanoseconds or less. Iron filings are not responsive to these rapid changes and cannot align themselves with the constantly changing electromagnetic waves.
To visualize electromagnetic waves, other methods such as using antennas, detectors, or specialized instruments are employed. These devices are designed to detect and measure the electric and magnetic fields associated with electromagnetic waves, but iron filings are not suitable for this purpose.