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GATE Electronics and Communications (EC) 2019 Solved Paper
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© examsnet.com
Question : 40
Total: 65
A germanium sample of dimensions
1
c
m
×
1
c
m
is illuminated with a
20
m
W
,
600
n
m
laser light source as shown in the figure. The illuminated sample surface has a 100 nm of loss-less Silicon dioxide layer that reflects one-fourth of the incident light. From the remaining light, one-third of the power is reflected from the Silicon dixodieGermanium interface, one-third is absorbed in the Germanium layer, and one-third is transmitted through the other side of the sample. If the absorption coefficient of Germanium at
600
n
m
is
3
×
10
4
c
m
−
1
and the bandgap is
0.66
e
V
, the thickness of the Germanium layer, rounded off to 3 decimal places, is ____________
µ
m
.
Your Answer:
Validate
Solution:
1
−
e
−
α
x
=
0.5
e
−
α
x
=
0.5
now
∝
=
3
×
10
4
c
m
−
1
∴
x
=
−
ln
(
0.5
)
3
×
10
4
© examsnet.com
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