MCQs on Solid State Electronic Devices – Light Emitting Diode and Optical Isolation
1 - Question
Who developed the first Light emitting diode?
a) Nick brown
b) Nick Holonyak
c) Stefencolumbus
d) Billy Stern
View Answer
Explanation: The first LED was developed by Nick Holonyak in the year 1962. He is a 91 year old American engineer and educator, widely known for his work on Light emitting diodes and was the first one to create the first visible LED.
2 - Question
Who was/were awarded with noble prize in physics in the year 2014 for the invention of blue light emitting diodes?
a) Hiroshi Amano
b) Nick Holonyak
c) Isamu Akasaki, Hiroshi Amano
d) Isamu Akasaki, Hiroshi Amano and Shuji Nakamura
View Answer
Explanation: The noble prize in physics in the year 2014 was awarded to a trio scientists of United states and japan, Isamu Akasaki, Hiroshi Amano and Shuji Nakamura for the invention of blue light emitting diodes.
3 - Question
Which alloy is used for green blue and white LED’s?
a) InGaN (Indium gallium nitride)
b) GaAs (Gallium arsenide)
c) (AlGaInP) Aluminum gallium indium phosphide
d) TiO2(titanium dioxide)
View Answer
Explanation: InGaN (Indium gallium nitride) alloy is used for green blue and white LED’s. Colour emitted by an LED depends on the type of Semiconductor materials used and also the proportion of the semiconductors used in the alloy.
4 - Question
Which alloy is used for red, orange and yellow LED’s?
a) InGaN (Indium gallium nitride)
b) GaAs (Gallium arsenide)
c) (AlGaInP) Aluminum gallium indium phosphide
d) TiO2(titanium dioxide)
View Answer
Explanation: (AlGaInP) Aluminum gallium indium phosphidealloy is used for red, orange and yellow LED’s. Colour emitted by an LED depends on the type of Semiconductor materials used and also the proportion of the semiconductors used in the alloy. advertisement
5 - Question
Recombination of charge carriers in an LED, releases some energy which comes out in the form of light.
a) True
b) False
View Answer
Explanation: Recombination of charge carriers in an LED, releases some energy which comes out in the form of light. The energy emitted by the recombination of charge carriers hits a layer of phosphor, this phosphor shows the properties of luminescence when charged, which is emitted in the form of visible light.
6 - Question
Opto-isolator uses a source of light for transmission, most commonly “near infrared light emitting diodes”.
a) True
b) False
View Answer
Explanation: Opto-isolator uses a source of light for transmission, most commonly “near infrared light emitting diodes”. An opto-isolator transmits signals through this source of light which passes through an isolated dielectric channel and is finally fetched by the photosensor(receiver).
7 - Question
LASER stands for ____
a) Light amplification by systematic emission of radiation
b) Light amplification by stimulated emission of radiation
c) Light absorption by stimulated emission of radiation
d) Low amplification by stimulating emitted radiation
View Answer
Explanation: LASER stands for “Light amplification by stimulated emission of radiation”. Laser or laser diodes are similar to the light emitting diodes as it directly produces light when voltage is applied across the terminals. The difference is that the light which it radiates is amplified by stimulated emission.
8 - Question
Which is a type of Opto-isolator?
a) CMCP793V-500
b) MOC3021
c) MPU 6050
d) L298N
View Answer
Explanation: MOC3021 is a type of Opto-isolator. CMCP793V-500 is a type of velocity sensor. MPU 6050 is a 6 axis gyroscope and accelerometer. L298N is a motor driver with dual-H bridge.
9 - Question
Optical isolator is also called as ________
a) Opaque isolator
b) Optical coupling
c) Optocoupler
d) Optical resistor
View Answer
Explanation: Optical isolator is also called as Optocoupler. Optical isolator’s are devices that transfer electrical signals between two isolated circuit by using light. They prevent damages to the system due to very high input voltage.
10 - Question
Which electromagnetic rays is emitted GaAs LED’s ?
a) Infrared
b) Visible light
c) Ultraviolet
d) Radio
View Answer
Explanation: Light emitting diodes made of Gallium arsenide alloy(GaAs) emits infrared rays or infrared light. The wavelength of the emitted rays is in the range of 850 nano-meters to 940 nano-meters.
11 - Question
Who is known as the father of fibre optics?
a) Nick brown
b) Nick Holonyak
c) Stefencolumbus
d) Narinder Singh Kapany
View Answer
Explanation: Narinder Singh Kapany is known as the father of fibre optics. This title is given to him for his amazing work towards fibre optics. He is an Indian born American physicist who was also a former Indian Ordnance Factories Service officer.
12 - Question
Which layer is just present above core that protects the light from going outside?
a) Core
b) Cladding
c) Coating
d) Mine
View Answer
Explanation: Cladding is just present above core that protects the light from going outside. It is made up optically transparent material with higher refractive index than that of core, which results the light to bounce due to total internal reflection.
13 - Question
Which layer is just present above cladding that protects the optical fibre from physical damage?
a) Core
b) Cladding
c) Coating
d) Cover
View Answer
Explanation: Coating is just present above cladding that protects the optical fibre from physical damage. They are usually made up of optically opaque materials. No light can pass through it either from inside or outside.
14 - Question
What is the working principle of optical fiber?
a) Total internal refraction
b) Total internal reflection
c) Lenz Law
d) Brine theory
View Answer
Explanation: The optical fiber works on the principle of Total internal reflection. It occurs when the angle of incidence of the incoming light ray is greater than the critical angle. It occurs when the light travels between two mediums of different refractive index.
15 - Question
The critical angle in total internal reflection depends on the colour of the incident light.
a) True
b) False
View Answer
Explanation: The critical angle in total internal reflection depends on the colour of the incident light. Different lights of different colours have different wavelengths and therefore the refractive index changes, so ultimately the critical angle also changes.