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## Sunday 21 February 2021

### CBSE Class 11 Physics - MCQ and Online Tests - Unit 15 - Waves

#### CBSE Class 11 Physics – MCQ and Online Tests – Unit 15 – Waves

Every year CBSE schools conducts Annual Assessment exams for 6,7,8,9,11th standards. These exams are very competitive to all the students. So our website provides online tests for all the 6,7,8,9,11th standard’s subjects. These tests are also very effective and useful for those who preparing for any competitive exams like Olympiad etc. It can boost their preparation level and confidence level by attempting these chapter wise online tests.

These online tests are based on latest CBSE syllabus. While attempting these our students can identify the weak lessons and continuously practice those lessons for attaining high marks. It also helps to revise the NCERT textbooks thoroughly.

#### CBSE Class 11 Physics – MCQ and Online Tests – Unit 15 – Waves

Question 1.
A whistle giving out 450 Hz approaches a stationary observer at a speed of 33 m/s. The frequency heard by the observer in Hz is
(a) 409
(b) 429
(c) 517
(d) 500

Answer

Answer: (d) 500

Question 2.
When a compression is incident on rigid wall it is reflected as
(a) Compression with a phase change of p
(b) Compression with no phase change
(c) Rarefaction with a phase change of p
(d) Rarefaction with no phase change

Answer

Answer: (a) Compression with a phase change of p

Question 3.
With the increase in temperature, the frequency of the sound from an organ pipe
(a) Decreases
(b) Increases
(c) Remain unchanged
(d) Changes erratically

Answer

Answer: (b) Increases

Question 4.
Loudness of a note of sound is
(a) Directly proportional to amplitude of the wave
(b) Directly proportional to square of amplitude of wave
(c) Directly proportional to velocity of the wave
(d) Directly proportional to square of velocity of the wave

Answer

Answer: (b) Directly proportional to square of amplitude of wave

Question 5.
The frequency of the note produced by plucking a given string increases as
(a) The length of the string increases
(b) The tension in the string increases
(c) The tension in the string decreases
(d) The mass per unit length of the string increases

Answer

Answer: (b) The tension in the string increases

Question 6.
A siren placed at a railway platfrom is emitting sound of frequency 5 kHz. A passenger sitting in a moving train A records a frequency of 5.5 kHz while the train approaches the siren. During his return journey in a different train B he records a frequency of 6.0 kHz while approaching the same siren. The ratio of velocity of train B to that of train A is
(a) 242 / 252
(b) 2
(c) 5 / 6
(d) 11 / 6

Answer

Answer: (b) 2

Question 7.
Energy is not carried by
(a) Longitudinal progressive waves
(b) Electromagnetic waves
(c) Transverse progressive waves
(d) Stationary wave

Answer

Answer: (d) Stationary wave

Question 8.
The extension in a string, obeying Hookes law is X. The speed of sound in the stretched string is V. If the extension in the string is increased to 1.5 X, the speed of sound will be
(a) 1.22 V
(b) 0.61 V
(c) 1.50 V
(d) 0.75 V

Answer

Answer: (a) 1.22 V

Question 9.
Energy is to be carried from one place to another. Which one of the following cannot be used?
(a) Longitudinal progressive waves
(b) Transverse progressive waves
(c) Electromagnetic waves
(d) Standing (stationary) waves

Answer

Answer: (d) Standing (stationary) waves

Question 10.
To demonstrate the phenomenon of beats we need
(a) Two sources which emit radiation of nearly the same frequency
(b) Two sources which emit radiation of exactly the same frequency
(c) Two sources which emit radiation of exactly the same frequency and have a definite phase relationship
(d) Two sources which emit radiation of exactly the same wavelength

Answer

Answer: (a) Two sources which emit radiation of nearly the same frequency

Question 11.
Four wires of identical lengths, diameters and material and stretched on a sonometer box. The ratio of their tension is 1 : 4 : 9 : 16. the ratio of their fundamental frequencies is
(a) 1 : 6 : 9 : 16
(b) 4 : 3 : 2 : 1
(c) 1 : 2 : 3 : 4
(d) 1 : 4 : 9 : 16

Answer

Answer: (c) 1 : 2 : 3 : 4

Question 12.
A resonance air column of length 40 cm resonates with a tuning fork of frequency 450 Hz. Ignoring end correction, the velocity of sound in air will be
(a) 720 m/s
(b) 820 m/s
(c) 920 m/s
(d) 1020 m/s

Answer

Answer: (a) 720 m/s

Question 13.
An observer is moving towards a stationary source of frequency 250 Hz with a velocity of 40 m/s. If the velocity of sound is 330 m/s, the apparent frequency heard by the observer will be
(a) 320 Hz
(b) 300 Hz
(c) 280 Hz
(d) 260 Hz

Answer

Answer: (c) 280 Hz

Question 14.
String is in fundamental mode of vibration then velocity is directly proportional to _______
(a) Square root of tension
(b) Square root of length
(c) Square of tension
(d) Square root of linear density

Answer

Answer: (a) Square root of tension

Question 15.
With the increase in temperature, the frequency of the sound from an organ pipe
(a) Decreases
(b) Increases
(c) Remain unchanged
(d) Changes erratically

Answer

Answer: (b) Increases

Question 16.
To demonstrate the phenomenon of beats we need
(a) Two sources which emit radiation of nearly the same frequency
(b) Two sources which emit radiation of exactly the same frequency
(c) Two sources which emit radiation of exactly the same frequency and have a definite phase relationship
(d) Two sources which emit radiation of exactly the same wavelength

Answer

Answer: (a) Two sources which emit radiation of nearly the same frequency

Question 17.
Transverse are generated in two uniform wires A and B by attaching their free ends to a vibrating source of frequency 600 Hz. The diameter of wire A is one-third that of wire B and tension in the wire A is double that in wire B. What is the ratio of velocities of waves of waves in wire A and B?
(a) v3 : 2
(b) 2 : v3
(c) 3 : v2
(d) v2 : 3

Answer

Answer: (d) v2 : 3

Question 18.
The extension in a string, obeying Hookes law is X. The speed of sound in the stretched string is V. If the extension in the string is increased to 1.5 X, the speed of sound will be
(a) 1.22 V
(b) 0.61 V
(c) 1.50 V
(d) 0.75 V

Answer

Answer: (a) 1.22 V

Question 19.
The equation of wave traveling along string is y = 3 cos p (100t – x) in C.G.S. unit then wavelength is
(a) 1 m
(b) 2 cm
(c) 5 cm
(d) None of above

Answer

Answer: (b) 2 cm

Question 20.
A resonating column of air contains
(a) Stationary longitudinal waves
(b) Stationary transverse waves
(c) Transverse progressive waves
(d) Longitudinal progressive waves

Answer

Answer: (a) Stationary longitudinal waves

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