An engineer or scientist is detecting heat escaping from a building. (a) Name a suitable electromagnetic band and explain one useful property. (b) State one possible hazard of sufficiently intense exposure to that band. (c) State the speed of this radiation in vacuum and explain whether it needs a material medium.

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infrared; a sensor detects the thermal radiation emitted by warm surfaces; intense infrared sources can cause burns; vacuum speed 3.0 × 10⁸ m/s; no medium required. A suitable choice is infrared. Its usefulness is linked to how the radiation interacts with matter: a sensor detects the thermal radiation emitted by warm surfaces. Naming the band without connecting a property to the proposed use is not a complete explanation. A relevant hazard is that intense infrared sources can cause burns. Risk depends on factors including intensity and exposure time, so a useful application does not mean every level of exposure is harmless. Like every electromagnetic band, this radiation travels at 3.0 × 10⁸ m/s in vacuum. Different bands have different wavelengths and frequencies, but they do not have different vacuum propagation speeds. Electromagnetic radiation does not require vibrating material particles to carry the disturbance. It can therefore travel through a vacuum, unlike sound, which requires a material medium and cannot propagate through empty space.

Electromagnetic radiation for detecting heat escaping from a building

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