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# HC Verma solutions for Class 12 Concepts of Physics 1 chapter 21 - Speed of Light [Latest edition]

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#### Chapters ## Chapter 21: Speed of Light

#### HC Verma solutions for Class 12 Concepts of Physics 1 Chapter 21 Speed of Light Exercise Short Answers [Pages 447 - 448]

Short Answers | Q 1 | Page 447

The speed of sound in air is 332 m s−1. Is it advisable to define the length 1 m as the distance travelled by sound in 1/332 s?

Short Answers | Q 2 | Page 447

Consider Galileo's method of measuring the speed of light using two lanterns. To get an accuracy of about 10%, the time taken by the experimenter in closing or opening the shutter should be about one tenth of the time taken by the light in going from one experimenter to the other. Assume that it takes 1/100 second for an experimenter to close or open the shutter. How far should the two experimenters be to get a 10% accuracy? What are the difficulties in having this separation?

Short Answers | Q 3 | Page 447

In Fizeau method of measuring the speed of light, the toothed wheel is placed in the focal plane of a converging lens. How would the experiment be affected if the wheel is slightly away from the focal plane?

Short Answers | Q 4 | Page 448

In the original Fizeau method, the light travelled 8.6 km and then returned. What could be the difficulty if this distance is taken as 8.6 m?

Short Answers | Q 5 | Page 448

What is the advantage of using a polygonal mirror with larger number of faces in Michelson method of measuring the speed of light?

#### HC Verma solutions for Class 12 Concepts of Physics 1 Chapter 21 Speed of Light Exercise MCQ [Page 448]

MCQ | Q 1 | Page 448

Light passes through a closed cylindrical tube containing a gas. If the gas is gradually pumped out, the speed of light inside the tube will

• increase

• decrease

• remain constant

• first increase and then decrease

MCQ | Q 2 | Page 448

The speeds of red light and yellow light are exactly same

• in vacuum but not in air

• in air but not in vacuum

• in vacuum as well as in air

• neither in vacuum nor in air

MCQ | Q 3 | Page 448

An illuminated object is placed on the principal axis of a converging lens so that a real image is formed on the other side of the lens. If the object is shifted a little,

• the image will be shifted simultaneously with the object

• the image will be shifted a little later than the object

• the image will be shifted a little earlier than the object

•  the image will not shift

#### HC Verma solutions for Class 12 Concepts of Physics 1 Chapter 21 Speed of Light Exercise MCQ [Page 448]

MCQ | Q 1 | Page 448

The speed of light is 299, 792, 458 ms−1
(a) with respect to the earth
(b) with respect to the sun
(c) with respect to a train moving on the earth
(d) with respect to a spaceship going in outer space.

MCQ | Q 2 | Page 448

Which of the following methods can be used to measure the speed of light in laboratory?

• Roemer method

• Fizeau method

• Foucault method

• Michelson method

MCQ | Q 3 | Page 448

Which of the following methods can be used to measure the speed of light in water?

• Roemer method

• Fizeau method

• Foucault method

•  Michelson method

#### HC Verma solutions for Class 12 Concepts of Physics 1 Chapter 21 Speed of Light [Page 448]

Q 1 | Page 448

In an experiment to measure the speed of light by Fizeau's apparatus, following data are used: Distance between the mirrors = 12.0 km,
Number of teeth in the wheel = 180.
Find the minimum angular speed of the wheel for which the image is not seen.

Q 2 | Page 448

In an experiment with Foucault's apparatus, the various distances used are as follows:
Distance between the rotating and the fixed mirror = 16 m
Distance between the lens and the rotating mirror = 6 m,
Distance between the source and the lens = 2 m.
When the mirror is rotated at a speed of 356 revolutions per second, the image shifts by 0.7 mm. Calculate the speed of light from these data.

Q 3 | Page 448

In a Michelson experiment for measuring speed of light, the distance travelled by light between two reflections from the rotating mirror is 4.8 km. The rotating mirror has a shape of a regular octagon. At what minimum angular speed of the mirror (other than zero) the image is formed at the position where a nonrotating mirror forms it?

## Chapter 21: Speed of Light ## HC Verma solutions for Class 12 Concepts of Physics 1 chapter 21 - Speed of Light

HC Verma solutions for Class 12 Concepts of Physics 1 chapter 21 (Speed of Light) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the CBSE Class 12 Concepts of Physics 1 solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Class 12 Concepts of Physics 1 chapter 21 Speed of Light are Principle of Superposition of Waves, Corpuscular Theory, Speed of Light, Coherent and Incoherent Sources and Sustained Interference of Light, Interference of Light Waves and Young’S Experiment, Reflection and Refraction of Plane Wave at a Plane Surface Using Wave Fronts, Huygens Principle, Introduction of Wave Optics, The Validity of Ray Optics, Seeing the Single Slit Diffraction Pattern, The Single Slit, The Doppler Effect, Reflection of a Plane Wave by a Plane Surface, Refraction at a Rarer Medium, Refraction of a Plane Wave, Refraction of Monochromatic Light, Law of Malus, Width of Central Maximum, Polarisation, Resolving Power of Microscope and Astronomical Telescope, Interference, Proof of Laws of Reflection and Refraction Using Huygen'S Principle, Brewster's Law, Plane Polarised Light, Fraunhofer Diffraction Due to a Single Slit, Coherent and Incoherent Addition of Waves.

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