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| 1. |
The wavelength of light in the visible region is about 390 nm for violet colour, about 550 nm (average wavelength) for yellow-green colour and about 760 nm for red colour. From which of the photosensitive materials with work functions listed given below and using the results of (i), (ii) and (iü) of (a), can you build a photoelectric device that operates with visible light ? |
| Answer» SOLUTION :For a photoelectric device to OPERATE, we REQUIRE INCIDENT light energy E to be equal to or GREATER than the work function `phi_(0)`, of the material. Thus, the photoelectric device will operate with violet light (with E = 3.19 eV) photosensitive material Na (with `phi_(0) = 2.75` eV), K (with `phi_(0)= 2.30` eV) and Cs (with `phi_(0) = 2.14` eV). It will also operate with yellow-green light (with E = 2.26 eV) for Cs (With `phi_(0)= 2.14` eV) only. However, it will not operate with red light (with E = 1.64 eV) for any of these photosensitive materials | |