Optics (Physics) Part-I

Total Questions: 50

31. Optical fibre works on the principle of : [U.P.U.D.A./L.D.A. (Pre) 2010, U.P.P.C.S. (Spl.) (Pre) 2008, I.A.S. (Pre) 1995]

Correct Answer: (a) Total internal reflection
Solution:

The optical fibre is a very thin strand of glass (silica) or plastic cable for transmitting light from one point to another. It works on the principle of total internal reflection. There is no loss of signal through an optical fibre.

32. The phenomenon used in optical fiber for transmission of light energy is [U.P.P.C.S. (Pre) 2019]

Correct Answer: (a) Total internal reflection
Solution:

The optical fibre is a very thin strand of glass (silica) or plastic cable for transmitting light from one point to another. It works on the principle of total internal reflection. There is no loss of signal through an optical fibre.

33. Which one of the following phenomenon is used in optical fibres? [U.P.P.C.S. (Mains) 2015]

Correct Answer: (c) Total internal reflection
Solution:

The optical fibre is a very thin strand of glass (silica) or plastic cable for transmitting light from one point to another. It works on the principle of total internal reflection. There is no loss of signal through an optical fibre.

34. In fiber-optic communication, the signal travels in the form of- [R.A.S/R.T.S.(Pre) 2012]

Correct Answer: (a) Lightwave
Solution:

Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fibre.

35. Consider the following statements: [U.P.P.C.S. (Pre) 2003, 2001, U.P.U.D.A./L.D.A. (Pre) 2002]

1. Fibre optics is based on the principle of total internal reflection.

2. In an optical fibre communication system, power consumption is extremely low.

3. Optical fibre communications are free from radio frequency interference.

4. In India, Reliance Group of Industries is engaged in the manufacture of the optical fibre.

Which of these statements are correct:

Correct Answer: (a) 1, 2 and 3
Solution:

Optical fibres are very thin, flexible and transparent cables made up of glass (silica) or plastic cable. They work on the principle of total internal reflection. In an optical fibre communication system, power consumption is extremely low.

They are free from radio frequency and electromagnetic interferences. In India, Sterlite-Tech company started manufacturing of optical fibre in the year 2000, not Reliance Group. Thus, option (a) is correct.

36. 'Endoscope' used by the doctors for examining the inside of patient's stomach, works on the principle of- [U.P. Lower Sub. (Pre) 2009]

Correct Answer: (d) Total internal reflection of light
Solution:

Endoscopes are widely used to examine the interior of a hollow organ or cavity of the body. They are based on the principle of total internal reflection within a fibre optic bundle of fibres.

37. An endoscope is used by a physician to view the internal parts of a body organ. It is based on the principle of - [U.P.P.C.S. (Pre) 2010, U.P.P.C.S. (Mains) 2009, U.P.P.C.S. (Spl.) (Mains) 2008, I.A.S. (Pre) 1999]

Correct Answer: (c) Total internal reflection of light
Solution:

Endoscopes are widely used to examine the interior of a hollow organ or cavity of the body. They are based on the principle of total internal reflection within a fibre optic bundle of fibres.

38. The reason of mirage is [U.P.P.C.S.(Pre) 1995, 2012]

Correct Answer: (d) Total internal reflection of light
Solution:

The mirage is caused by the refraction and total internal reflection of light at layers of air of different densities. In Desert areas, the successive upper layer is denser than those below there due to terrestrial heating. A ray of light coming from a distant object, like the top of a tree gets refracted from a denser to a rarer medium.

Consequently, the refracted ray bends away from the normal until at a particular layer, the light is incident at an angle greater than the critical angle. At this stage, the incident ray suffers total internal reflection and enters the eyes of the observer. It appears as if an inverted image of the tree.

39. Mirage formation is an example of - [U.P.P.C.S. (Mains) 2014, U.P.U.D.A./L.D.A. (Pre) 2013, U.P. Lower Sub. (Mains) 2013]

Correct Answer: (c) Total internal reflection
Solution:

The mirage is caused by the refraction and total internal reflection of light at layers of air of different densities. In Desert areas, the successive upper layer is denser than those below there due to terrestrial heating. A ray of light coming from a distant object, like the top of a tree gets refracted from a denser to a rarer medium.

Consequently, the refracted ray bends away from the normal until at a particular layer, the light is incident at an angle greater than the critical angle. At this stage, the incident ray suffers total internal reflection and enters the eyes of the observer. It appears as if an inverted image of the tree.

40. Consider the following natural phenomena : [I.A.S. (Pre) 2002]

1. Terrestrial heating

2. Reflection of light

3. Refraction of light

4. Diffraction of light

Due to which of these phenomena is mirage formed ?

Correct Answer: (c) 1 and 3
Solution:

The mirage is caused by the refraction and total internal reflection of light at layers of air of different densities. In Desert areas, the successive upper layer is denser than those below there due to terrestrial heating. A ray of light coming from a distant object, like the top of a tree gets refracted from a denser to a rarer medium.

Consequently, the refracted ray bends away from the normal until at a particular layer, the light is incident at an angle greater than the critical angle. At this stage, the incident ray suffers total internal reflection and enters the eyes of the observer. It appears as if an inverted image of the tree.