GATE (Graduate Aptitude Test in Engineering) Electronics & CE (EC): Questions 769 - 772 of 1602
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Passage
Optical fibre communication is one among the new techniques have come up and are extensively used for communication purposes. The portion of the e. m. spectrum encompasses the optical region falls in the wavelength of 50 nm (Ultraviolet) to approximately 100 µm (Infrared) which includes visible light spectrum from 400 nm (Violet) to 700 nm (Red) . The order of frequency corresponding to these wavelengths falls in the range to Hz. There are two types of transmission media used for optical communication i.e.. , atmospheric channel and guided wave channel. Out of the two, guided wave channel provide much more reliable and versatile medium of communication. The medium used for guided channels in optical range are non-metallic guides popularly known as optical fibre. The optical fibre link used for communication applications has several advantages over conventional cupper cable links which makes possible to send much more data over long distances with negligible attenuation. Although some difficulties do exist in the making of optical fibre set and there are some challenges being faced yet this type of communication mechanism has made a great impact in the present scenario.
Question 769 (3 of 4 Based on Passage)
Appeared in Year: 2014
Question MCQ▾
When atoms in Direct bandgap semiconductors move from higher energy state () to lower energy state () and emission of light takes place, the energy of emitted photon is given as (December)
Choices
Choice (4) | Response | |
---|---|---|
a. | ||
b. | ||
c. | ||
d. |
Question 770 (4 of 4 Based on Passage)
Appeared in Year: 2014
Question MCQ▾
The following are correct about a semiconductor LASER: (December)
1. It requires population inversion
2. It has shorter lifetime than LED
3. It demonstrates spontaneous emission phenomenon
4. It generates monochromatic incoherent light.
Find out the correct answer:
Choices
Choice (4) | Response | |
---|---|---|
a. | 1 & 2 | |
b. | 2 & 4 | |
c. | 1 & 4 | |
d. | 1 & 3 |
Question 771
Appeared in Year: 2014
Question Assertion-Reason▾
Assertion(Ꭺ)
The two types of optical sources used in transmitter of optical communication link are LED and LASER. (December)
Reason(Ꭱ)
LASERs are costly hence not preferred for small distance low cost systems.
Choices
Choice (4) | Response | |
---|---|---|
a. | Both Ꭺ and Ꭱ are true but Ꭱ is NOT the correct explanation of Ꭺ | |
b. | Ꭺ is false but Ꭱ is true | |
c. | Both Ꭺ and Ꭱ are false | |
d. | Both Ꭺ and Ꭱ are true and Ꭱ is the correct explanation of Ꭺ |
Question 772
Appeared in Year: 2014
Question Match List-Ⅰ List-Ⅱ▾
Match the following lists: (December)
List-Ⅰ (Column-I) | List-Ⅱ (Column-II) |
---|---|
(A) DSB-SC modulation | (i) Weaver՚s method |
(B) SSB-modulation | (ii) Envelope detection |
(C) Phase-shift detection | (iii) Balanced modulator |
(D) AM-demodulation | (iv) Foster Seeley |
Choices
Choice (4) | Response | |
---|---|---|
| ||
a. |
| |
b. |
| |
c. |
| |
d. |
|