Test: Optical Absorption - Electronics and Communication Engineering (ECE) MCQ

Current generated I = P₀ × R
Given P₀ = 4 mw

Incident power = 20 mW = P_i

Reflected power (P_r) from SiO₂ is one-fourth, i.e

Power left will be:

From this  power, the power reflected from Ge Interface is:

Now, the power absorbed in the Germanium layer is:

Power Transmitted through the other side of the sample is:

The power entering Germanium Sample = Power absorbed + Power Transmitted, i.e.

α = absorption coefficient

Concept:

The amount of energy released or absorbed is given by
E = mL
where m is the mass of the substance and L is the Latent Heat.

Solution:
Energy used in the conversion of ice to water is given by 
⇒ mL = 1000 g x 80 cal g^-1 = 80000 cal
The energy of the photon absorbed is given by
⇒ nT x E = nT x hν
⇒ nThν = mL

In some common semiconductors, there is a variation in absorption curves for materials. It is found that they are each suitable for different wavelength and related applications. This is due to difference in band gap energies. Thus absorption coefficient depends on wavelength.