Physics20815 marksNumerical: energy gap wavelengthconductors, insulators and semiconductors
The energy gaps of some alkali halides are KCl = 7.6 eV, KBr = 6.3 eV, KI = 5.6 eV. Which of these are transparent to visible light? At what wavelength does each become opaque?
The energy gaps of some alkali halides are KCl = 7.6 eV, KBr = 6.3 eV, KI = 5.6 eV. Which of these are transparent to visible light? At what wavelength does each become opaque? [5]
- Energy gap of KCl: $Eg = 7.6$ eV - Energy gap of KBr: $Eg = 6.3$ eV - Energy gap of KI: $Eg = 5.6$ eV - Visible light range: $\lambda \approx 4000$ Å to $7000$ Å - Constants: $h = 6.62 \times 10^{-34}$ J·s, $c = 3 \times 10^8$ m/s, $1\text{ eV} = 1.6 \times 10^{-19}$ J A material is transparent...