BAND-GAP ENERGY of a semiconductor crystal determines the energy of the photons it emits and thus the wavelength of the light those photons produce.
(BAND-GAP ENERGY of a semiconductor crystal; determines; the energy of the photons) (the photons; emits; it) (the light; produce; those photons)
BAND-GAP ENERGY of a semiconductor crystal the photons the light
determines emits produce
the energy of the photons
it
those photons