Semiconducting Devices Question 25
Question: Assertion : A P-N photodiode is made from a semiconductor for which Eg = 2.8 eV. This photo diode will not detect the wavelength of 6000 nm. Reason : A PN photodiode detect wavelength l if $ \frac{hc}{\lambda }>E _{g} $ .
Options:
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.
Show Answer
Answer:
Correct Answer: A
Solution:
For detection of a particular wavelength (l) by a PN photo diode, energy of incident light > Eg
Therefore $ \frac{hc}{E _{g}}>\lambda $ For $ E _{g}=2.8eV,\frac{hc}{E _{g}}=\frac{6.6\times {{10}^{-34}}\times 3\times 10^{8}}{2.8\times 1.6\times {{10}^{-19}}}=441.9nm $ i.e.
$ \frac{hc}{E _{g}}<6000nm, $ so diode will not detect the wavelength of 6000Å.
