Physics (Part-II) (UPSC)

Total Questions: 60

41. The technique used to transmit audio signals in television broadcasts is: [1995]

(a) Amplitude Modulation
(b) Frequency Modulation
(c) Pulse Code Modulation
(d) Time Division Multiplexing

Correct Answer: (b) Frequency Modulation

Solution:Frequency modulation It is a process in which the frequency of the carrier is varied in accordance with the instantaneous value of modulating voltage. In telecommunications and signal processing, frequency modulation (FM) conveys information over a carrier wave by varying its instantaneous frequency. FM is most commonly used for radio and television broadcasting.

42. Consider the following statements: [1996]

At the present level of technology available in India, solar energy can be conveniently used to:

1. Supply hot water to residential buildings.

2. Supply water for minor irrigation projects.

3. Provide street lighting.

4. Electrify a cluster of villages and small towns.

(a) 1, 2, 3 and 4 are correct
(b) 2 and 4 are correct
(c) 1 and 3 are correct
(d) 1, 2 and 3 are correct

Correct Answer: (c) 1 and 3 are correct

Solution:Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. At present solar energy in our country is used for solar water heater. Solar lights that charge during the day and light up at night are a common sight along walkways.

43. One astronomical unit is the average distance between : [1998]

(a) Earth and the Sun
(b) Earth and the Moon
(c) Jupiter and the Sun
(d) Pluto and the Sun

Correct Answer: (a) Earth and the Sun

Solution:An astronomical unit (AU) is defined specifically as the average distance between the Earth and the Sun, approximately 93 million miles or 150 million kilometres. The other options are incorrect because the AU does not pertain to the distances between the Earth and the Moon, Jupiter and the Sun, or Pluto and the Sun.

44. For reproducing sound, a CD (Compact Disc) audio player uses a: [2000]

(a) quartz crystal
(b) titanium needle
(c) laser beam
(d) barium titanate ceramic

Correct Answer: (c) laser beam

Solution:The laser beam reads the digital data encoded on the CD's surface by reflecting off pits and lands on the disc. This data is then converted into an audio signal. The other options are incorrect: a quartz crystal is used in timekeeping, a titanium needle is used in record players, and barium titanium ceramic is not used in CD players.

45. Which one of the following to operate a TV set? [2001]

(a) Light waves
(b) Sound waves
(c) Microwaves
(d) Radio waves

Correct Answer: (d) Radio waves

Solution:Radio waves are a type of electromagnetic radiation with wavelengths in the electromagnetic spectrum longer than infrared light. Like all other electromagnetic waves, they travel at the speed of light.

Artificially-generated radio waves are used for fixed and mobile radio communication, broadcasting, radar and other navigation systems, satellite communication, computer networks and innumerable other applications.

46. Consider the following statements: [2001]

In a nuclear reactor, self-sustained chain reaction is possible, because:

1. more neutrons are released in each of the fission reactions.

2. the neutrons immediately take part in the fission process.

3. the fast neutrons are slowed down by graphite.

4. every neutron released in the fission reaction initiates further fission.

Which of these statements are correct?

(a) 1, 2 and 3
(b) 1 and 3
(c) 2 and 4
(d) 2, 3 and 4

Correct Answer: (b) 1 and 3

Solution:In a nuclear reactor, more neutrons are indeed released in each fission reaction, and these fast neutrons are slowed down by a moderator like Graphite to sustain the chain reaction. Statement 2 is incorrect because neutrons do not immediately take part in the fission process; they need to be slowed down first. Statement 4 is also incorrect because not every neutron initiates further fission; some escape or are absorbed without causing fission.

47. Consider the following statements: [2005]

1. A geo-stationary satellite is at an approximate height of 10,000 km.

2. FM transmission of music is of very good quality because the atmospheric or man made noises which are generally frequency variations can do little harm.

Which of the statements give above is/are correct?

(a) 1 only
(b) 2 only
(c) Both 1 and
(d) Neither 1 nor 2

Correct Answer: (b) 2 only

Solution:The geostationary satellite is a satellite having a time-period of 24 hours. Using this time-period, the height of the satellite comes out to be approximately 35,800 km. FM broadcasting is a broadcast technology pioneered by Edwin Howard Armstrong that uses frequency modulation (FM) to provide high-fidelity sound over broadcast radio. FM transmission is quite immune to noise as compared to AM transmission. Noise is a form of amplitude variations in the transmitted signal due to atmosphere, industries, etc.

48. What does the term Dolby B or Dolby C printed on tape-recorders and other sound systems refer to: [2006]

(a) frequency Modulated System
(b) amplitude Modulated System
(c) noise Reduction Circuit
(d) both DC and AC power can be used

Correct Answer: (c) noise Reduction Circuit

Solution:Dolby B and C are the noise reduction circuits developed by Dolby laboratories. Dolby noise reduction has made it possible to protect the music from tape noise, and helped make cassette the most popular audio product ever devised.

49. Which of the following types is used by computed tomography employed for visualisation of the internal structure of human body? [2007]

(a) X-ray
(b) South waves
(c) Magnetic resonance
(d) Radio isotopes

Correct Answer: (a) X-ray

Solution:X-ray computed tomography (CT) is a medical imaging method employing tomography created by computer processing. This technique is used to generate a three-dimensional image of the inside of an object.

50. With reference to solar power production in India, consider the following statements: [2018-1]

1. India is the third largest in the world in the manufacture of silicon wafers used in photovoltaic units.

2. The solar power tariffs are determined by the Solar Energy Corporation of India.

Which of the statements given above is/are correct?

(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2

Correct Answer: (d) Neither 1 nor 2

Solution:There is no significant production of silicon wafers in India (as of 2011). So unlikely that it became 3rd largest by 2017-18. So, #1 is wrong.

Tariff's are determined under the Electricity Act. Any entity with "Corporation" word is irrelevant. so, #2 is wrong.

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