The band gap of silicon is 1.12 eV.

1. For what range of wavelengths will silicon be transparent? (See Example 29–5.) In what region of the electromagnetic spectrum does this transparent range begin?
2. If window glass is transparent for all visible wavelengths, what is the minimum possible band gap value for glass (assume $\lambda$ = 400 nm to 700 nm)? [Hint: If the photon has less energy than the band gap, the photon will pass through the solid without being absorbed.]