Use app×
Join Bloom Tuition
One on One Online Tuition
JEE MAIN 2025 Foundation Course
NEET 2025 Foundation Course
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
17.0k views
in Physics by (50.3k points)

(a) Three photo diodes D1, D2 and D3 are made of semiconductors having band gaps of 2.5 eV and 3 eV, respectively. Which of these will not be able to detect light of wavelength 600 nm? 

(b) Why photo diodes are required to operate in reverse bias? Explain.

1 Answer

+1 vote
by (51.1k points)
selected by
 
Best answer

(a) Photo diode is a semiconductor made of photosensitive semiconductor material. The conductivity of p-n function photo diode depends on the intensity of light falling on it.

Given:

• Band gap of photo diode D1 is 2.5 eV. 

• Band gap of photo diode D2 is 2 eV. 

• Bond gap of photo diode D3 is 3 eV.

Wavelength of the incident light is λ = 600 nm. Therefore, the energy of incident light is

where h is Planck’s constant, c is the speed of light. Therefore,

The photo diode is able to detect the light of wavelength 600 nm if the energy of incident radiation is more than the band gap of the photo diode. Therefore, D1 and D3 are not able to detect incident light.

(b) Photo diodes are required to operate in reverse bias because when a photo diode is reverse biased, the width of depletion region increases, and the function capacitance decreases. Thus, the response time of photo diode decreases making it faster. Photo diode is one of the fastest photo detectors.

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...