Does infrared radiation transmit through metals?

• A. Yes
• B. No
• C. Sometimes
• D. Only for very thin metals

Answer: (B)

Infrared radiation is not transmitted through metals because metals act as strong reflectors in the infrared. The free electrons in a metal respond to the oscillating electric field of the infrared wave, creating currents that reflect most of the incident light and convert a portion to heat. The depth that infrared waves can penetrate a metal—called the skin depth—is extremely small, so the wave hardly enters the bulk. As a result, bulk metals are opaque to infrared radiation.

So, the best answer is that infrared radiation does not transmit through metals. In practice, saying it transmits only in very thin films isn’t the typical behavior you rely on; metals are generally opaque to infrared even when thin, though extremely thin or nonuniform films can show minimal transmission under special conditions.