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1. This question is about photoelectric emission. A piece of metal is placed in an evacuated container. Light of wavelength 444 nm is incident on the surface of the metal. The surface has a work function of 4.60 eV. (a) (i) Calculate the energy, in joule, of a photon of light of wavelength 444 nm. (1) (ii) ( 11 Deduce whether photoelectric emission of electrons will occur. (3) ( (b) The wavelength of the light incident on the surface is now reduced to 222 nm. State and explain why electrons having a range of kinetic energy from zero to approximately 1.0 eV will be emitted.
In the photoelectric effect, electrons are emitted from a metal surface when light of a suitable frequency is incident on the surface. The diagram below shows an arrangement for investigating some aspects of the photoelectric effect. light P evacuated quartz tube μΑ variable de supply P and Q are metal plates. Monochromatic light of frequency fis incident on plate P. In the situation shown, the microammeter (UA) registers a current. The intensity of the light is kept constant throughout the experiment. (c) As the potential difference between P and Q is increased, the current in the circuit decreases until it is zero. State and explain the polarity of the metal plate Q.
(d) The potential difference in the circuit is increased until the current in the circuit just becomes zero. The potential difference is then kept constant. The frequency fof the light is increased to a new value and the intensity is kept constant. The microammeter again registers a current. Outline how Einstein's theory of the photoelectric effect accounts for this observation. (c) Explain why in (b) as fis increased at constant intensity, the current registered by the microammeter decreases.