This question concerns the photoelectric effect in a cosmic context. Ultraviolet radiation striking dust grains composed of the moon's dominant rock type, feldspar (with work function 4.5 eV), leaves them with a small electric charge. Smaller grains levitate due to the resulting electrostatic repulsion, giving the surface a diffuse dust halo. What sign of charge do the dust grains have? Negative Positive O Some grains are negative, some are positive.
