Ph Check Yourself 13.2 Why is glass transparent to visible light but opaque to ultraviolet and infrared?
The natural frequency of vibration for electrons in glass is the same as the frequency of ultraviolet light, so resonance in the glass occurs when ultraviolet waves shine on it. The absorbed energy is transferred to other atoms as heat, not reemitted as light, so the glass is opaque at ultraviolet frequencies. In the range of visible light, the forced vibrations of electrons in the glass are at smaller amplitudes--vibrations are more subtle, reemission of light (rather than the generation of heat) occurs, and the glass is transparent. Lower frequency infrared causes whole molecules, rather than electrons, to resonate; again, heat is generated and the glass is opaque.