A p-n photodiode is fabricated from a semiconductor with a bandgap of Can it detect a wavelength of 6000 nm?

No, the photodiode is unable to detect wavelengths of 6000 nm due to the following:

The energy bandgap of the given photodiode is given as

The wavelength has the value

The energy of the signal is represented by the following relation:

In the equation, is the Planck’s constant and is the speed of light .

Putting the values in the equation, we get

But,

Therefore,

A signal with a wavelength of 6000 nm has an energy of 0.207eV, which is less than the energy band gap of a photodiode, which is 2.8eV. As a result, the photodiode is unable to detect the signal.