Physics Group - II (3110018)

BE | Semester-1   Winter-2019 | 02-01-2020

Q4) (b) 

The transmitted intensity is 0.4 times intensity of incident light. If this light is incident on a semiconductor having a thickness of 0.5 cm then find absorption coefficient. 

Here,  Incident intensity = I0
          Transmitted intensity = I = 4 I0
          Thickness = d = 0.5 cm = 5 × 10-3 m
          Absorption coefficient = α 

Now, II0 = exp  -α d 

    ⇒0.4 × I0I0 = exp  -α d 

    ⇒ln 0. 4  = - α d

    ⇒α  = - ln 0. 4 d 

    ⇒α  = -  - 0.916 5 × 10-3 

    ⇒α  = 0.18 × 103 m-1

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