Optical Communication
Trending Questions
Q. Identify the electromagnetic waves whose wavelengths lie in the range
(a) 1011<λ<10−14m
(b) 10−4m<λ<10−6m
Write one uses of each.
(a) 1011<λ<10−14m
(b) 10−4m<λ<10−6m
Write one uses of each.
Q. A 100 m long antenna is mounted on a 500 m tall building. The complex can become a transmission tower for waves with λ :
- ∼ 400 m
- ∼ 425 m
- ∼ 150 m
- ∼ 2400 m
Q. For skywave propagation of a 10 MHz signal, what should be the minimum electron density in ionosphere?
- 1.2×1022 m−3
- 1.2×106 m−3
- 1.2×1012 m−3
- 1.2×1016 m−3
Q. Which one of the following layers of the atmosphere is responsible for the deflection of radio waves?
- Mesosphere
- Stratosphere
- Troposphere
- Ionosphere
Q. Frequencies higher than 10MHz are found not to be reflected by the particles present in the ionosphere then what is the maximum electron density of the ionosphere?
- 104em−3
- 1014em−3
- 101481em−3
- 10147em−3
Q.
Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
(a) 21 cm (wavelength emitted by atomic hydrogen in interstellar space).
(b) 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
(c) 2.7 K [temperature associated with the isotropic radiation filling all space thought to be a relic of the big-bang origin of the universe].
(d) 5890˚A−5896˚A [double lines of sodium]
(e) 14.4 ke V [energy of a particular transition in 57Fe nucleus associated with a famous high resolution spectroscopic method (M¨ossbauer spectroscopy)].
Q. If critical frequency for ionosphere is 30MHz. Calculate the maximum frequency which can come back on earth if transmitted at an angle 600 from vertical position:
- 40MHz
- 15MHz
- 30MHz
- 60MHz
Q. Name the Stephen Hawking project which detected 15 short radio bursts from space.
- Breakthrough Mission
- Breakthrough Action
- Breakthrough Listen
- Breakthrough Communication
Q. Transmission via sky waves is impossible for the frequencies
- less than 40MHz
- equal to 40MHz
- more than 40MHz
- all of the above
Q. Beyond which frequency, the ionosphere bends any incident electromagnetic radiation but do not reflect it back towards the earth?
- 50 MHz
- 40 MHz
- 30 MHz
- 20 MHz
Q. In biprism experiment, the distance of 20th bright band from the centre of the interference pattern is 8 mm. The distance of the 30th bright band is
- 4 mm
- 8 mm
- 12 mm
- 16 mm
Q. Electrons of 10 KeV strike a tungsten target. The radiations emitted by it are
- Visible light.
- X-rays.
- Radio waves.
- Infrared radiations.
