Sodium and potassium coated surfaces emit electrons when exposed to light.

Explanation

Here's the explanation:Photoelectric Effect:Sodium and potassium, along with other alkali metals like caesium, exhibit the photoelectric effect. This phenomenon involves the emission of electrons from a material's surface when exposed to light of sufficiently high energy (frequency or photon energy).Wavelength Threshold:Each material has a threshold wavelength below which light cannot cause electron emission. This threshold corresponds to the minimum energy required to dislodge an electron from its bound state in the atom.Wavelength Range for Sodium and Potassium:For sodium and potassium, the threshold wavelengths lie in the ultraviolet (UV) region of the electromagnetic spectrum. This means that only light with a shorter wavelength (higher frequency) than the threshold can eject electrons from these elements.Incorrect Options:(a) Infrared: Infrared radiation has a longer wavelength (lower frequency) than the threshold of sodium and potassium, hence it cannot emit electrons from these elements through the photoelectric effect.(b) Visible: While some visible light, particularly violet and blue, might have enough energy to exceed the threshold for certain materials, it generally doesn't meet the threshold for sodium and potassium.(d) Yellow: Yellow light has an even longer wavelength (lower frequency) than visible light, making it incapable of emitting electrons from sodium and potassium due to insufficient energy.