![]() ![]() When light intensity increases on the LDR surface, then its resistance decreases, and conductivity increases. LDR resistance and conductivity depend on the light. So the material conductivity increase and resistance decrease. Then, the bandgap of the semiconductor material to make the electrons jump from the valence band to the conduction band. When light intensity increases i.e There are more photons, so, the energy will increase. ![]() When light falls or photons fall on the semiconductor material, the electrons in the valence band of the semiconductor material are excited to the conduction band. It has a high resistance because there are very few electrons that are free and these free electrons can able move by external energy. It is made of semiconductor material that has high resistance. Photoconductivity is an optical phenomenon, when the material absorbed light then the material’s conductivity is increased. The Light Dependent Resistor or Photoresistor works on the principle of “ Photoconductivity”. Extrinsic photo resistors are mainly used for long wavelengths. So, less amount of energy is required to excite the electrons to move it to the conduction band. These impurities create a new energy band above the existing valence band which is filled with electrons. The Extrinsic photoresistor is made of semiconductor of materials doped with impurities. So, material conductivity will be increase and resistance will be decreased. When Photons fall on the LDR then the semiconductor material’s excited electrons move from the valence band to the conduction band and the number of charge carriers are increased. The intrinsic photoresistor is made of un-doped pure semiconductor materials such as silicon or germanium. These are Intrinsic photoresistors and Extrinsic photoresistors Photoresistor or LDR is categorized into two types based on the materials used to construct them. ![]()
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