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An LED made of Ga-As operates at a wavelength of 0.86 μm. The surrounding medium is air. The relative permittivity of Ga-As is 12.9. The external quantum efficiency of LED is

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UGC NET Paper 2: Electronic Science Nov 2017 Official Paper
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  1. 2.31%
  2. 23.1%
  3. 13.1%
  4. 1.31%

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Option 4 : 1.31%
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UGC NET Paper 1: Held on 21st August 2024 Shift 1
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The external quantum efficiency is defined as:

where n is the permittivity of the material.

= 3.59

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