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The spectral response of the light detector determines its sensitivity to different wavelengths in light spectrum. Thus, to increase the sensitivity, the spectral of source and the detector are matched.
The photo diode is connected in revearsed bias way. It operates by converting signals that hit the junction to a voltage or current. The junction uses and illumination window with an anti-reflect coating to absorb the light photons. The result of the absorption of photons is the creation of electron hole pairs.
When the light a above a cetain frequency strike on metal, electrons are escaped which are calld photoelectrons. The maximum kinetic energy depend on the frequency of light.The photoelectric effect can be explained by the particle behaviour of light. The photoelctric equation involves:
H = Plank constant
f = frequency of the light
Φ= the work function in joules(J) / minimum energy required to remove an electron fron teh surface of material.
Ek = the maximum kinetic enerygy of the emitted electrons in joules (J)
hf is the energy of a photon of light.
This equation can be rearranged as
Comparing with
By this second equation we can draw the graph as follows
Figure 3: Frequency graph
References
- Encyclopedia: Definition of:laser, Accessed:27.3.2014
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