A wavelength-sensitive detector is provided that is based on elongate nanostructures, e.g. nanowires. The elongate nanostructures are parallel with respect to a common substrate and they are grouped in at least first and second units of a plurality of parallel elongate nanostructures. The elongate nanostructures are positioned in between a first and second electrode, the first and second electrodes lying respectively in a first and second plane substantially perpendicular to the plane of substrate, whereby all elongate nanostructures in a same photoconductor unit are contacted by the same two electrodes. Circuitry is added to read out electrical signals from the photoconductor units. The electronic density of states of the elongate nanostructures in each unit is different, because the material, of which the elongate nanostructures are made, is different or because the diameter of the elongate nanostructures is different. Each unit of elongate nanostructures therefore gives a different response to incident photons such that wavelength-specific information can be derived with the device.