Optical devices manipulate light waves to enhance images for viewing or analyze light wave properties. They include stereoscopes for viewing stereoscopic photos, microscopes that use lenses to magnify small samples, and telescopes that gather and focus light to create magnified images. Optical devices also include prisms, projectors, polarimeters, and diffraction gratings that disperse light into spectra. Photovoltaic cells directly convert light into electricity at the atomic level through the photoelectric effect, using semiconductors treated to form an electric field that produces a current when electrons are knocked loose by light. Modules of connected solar cells supply electricity dependent on the amount of light striking them.