11th Physics - Book Back Answers - Unit 11 - English Medium Guides

 

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Tamil Nadu Board 11th Standard Physics - Unit 11: Book Back Answers and Solutions

    This post covers the book back answers and solutions for Unit 11 – Physics from the Tamil Nadu State Board 11th Standard Physics textbook. These detailed answers have been carefully prepared by our expert teachers at KalviTips.com.

    We have explained each answer in a simple, easy-to-understand format, highlighting important points step by step under the relevant subtopics. Students are advised to read and memorize these subtopics thoroughly. Once you understand the main concepts, you’ll be able to connect other related points with real-life examples and confidently present them in your tests and exams.

    By going through this material, you’ll gain a strong understanding of Physics Unit 11 along with the corresponding book back questions and answers (PDF format).

Question Types Covered:

• 1 Mark Questions: Choose the correct answer, Fill in the blanks, Identify the correct statement, Match the following 
• 2 Mark Questions: Answer briefly 
• 3, 4, and 5 Mark Questions: Answer in detail

All answers are presented in a clear and student-friendly manner, focusing on key points to help you score full marks.

All the best, Class 11 students! Prepare well and aim for top scores. Thank you!

Unit 11:Waves

I. Multiple Choice Questions

1. A student tunes his guitar by striking a 120 Hertz with a tuning fork, and simultaneously plays the 4^th  string on his guitar. By keen observation, he hears the amplitude of the combined sound oscillating thrice per second. Which of the following frequencies is the most likely the frequency of the 4^th  string on his guitar?
a) 130 
b) 117
c) 110 
d) 120
Answer Key:
b) 117

2. A transverse wave moves from a medium A to a medium B. In medium A, the velocity of the transverse wave is 500 ms^-1  and the wavelength is 5 m. The frequency and the wavelength of the wave in medium B when its velocity is 600 ms^-1 , respectively are
a) 120 Hz and 5 m
b) 100 Hz and 5 m
c) 120 Hz and 6 m
d) 100 Hz and 6 m
Answer Key:
d) 100 Hz and 6 m

3. For a particular tube, among six harmonic frequencies below 1000 Hz, only four harmonic frequencies are given : 300 Hz, 600 Hz, 750 Hz and 900 Hz. What are the two other frequencies missing from this list?.
a) 100 Hz, 150 Hz
b) 150 Hz, 450 Hz
c) 450 Hz, 700 Hz
d) 700 Hz, 800 Hz
Answer Key:
b) 150 Hz, 450 Hz

4. Which of the following options is correct?.

A	B
(1) Quality	(A) Intensity
(2) Pitch	(B) Waveform
(3) Loudness	(C) Frequency

Options for (1), (2) and (3), respectively are
a) (B),(C) and (A)
b) (C), (A) and (B)
c) (A), (B) and (C)
d) (B), (A) and (C)
Answer Key:
a) (B),(C) and (A)

5. Eqution of travelling wave on a stretched string of linear density 5 g/m is y = 0.03 sin(450t – 9x), where distance and time are measured in SI units. The tension in the string is
a) 5 N
b) 12.5 N
c) 7.5 N
d) 10 N
Answer Key:
b) 12.5 N

6. A sound wave whose frequency is 5000 Hz travels in air and then hits the water surface. The ratio of its wavelengths in water and air is
a) 4.30 
b) 0.23
c) 5.30 
d) 1.23
Answer Key:
a) 4.30 

7. A person standing between two parallel hills fires a gun and hears the first echo after t₁ sec and the second echo after t₂ sec. The distance between the two hills is
a) $\frac{\mathrm{v}({\mathrm{t}}_1-{\mathrm{t}}_2)}{2}$
b) $\frac{\mathrm{v}\left({\mathrm{t}}_1{\mathrm{t}}_2\right)}{2({\mathrm{t}}_1+{\mathrm{t}}_2)}$
c) $\frac{\mathrm{v}({\mathrm{t}}_1+{\mathrm{t}}_2)}{}$
d) $\frac{\mathrm{v}\left({\mathrm{t}}_{\mathrm{1+}}{\mathrm{t}}_2\right)}{2}$
Answer Key:
d) $\frac{\mathrm{v}\left({\mathrm{t}}_{\mathrm{1+}}{\mathrm{t}}_2\right)}{2}$

8. An air column in a pipe which is closed at one end, will be in resonance with the vibrating body of frequency 83Hz. Then the length of the air column is
a) 1.5 m 
(b) 0.5 m
(c) 1.0 m 
(d) 2.0 m
Answer Key:
(c) 1.0 m 

9. The displacement y of a wave travelling in the x direction is given by y=(2 x10−³  ) sin (300t−2x+ ) , where x and y are measured in metres and t in second. The speed of the wave is

(a) 150 ms^-1

(b) 300 ms^-1

(c) 450 ms^-1

(d) 600 ms^-1

Answer Key:
(a) 150 ms-1 

10. Consider two uniform wires vibrating simultaneously in their fundamental notes. The tensions, densities, lengths and diameter of the two wires are in the ratio 8 : 1, 1 : 2, x : y and 4 : 1 respectively. If the note of the higher pitch has a frequency of 360 Hz and the number of beats produced per second is 10, then the value of x : y is
(a) 36 : 35
(b) 35 : 36
(c) 1 : 1
(d) 1 : 2
Answer Key:
(a) 36 : 35

11. Which of the following represents a wave
(a) (x - vt)³  
(b) x(x+vt)
(c) $\frac{1}{(\mathrm{x}+\mathrm{vt})}$
(d) sin(x+vt)
Answer Key:
(d) sin(x+vt)

12. A man sitting on a swing which is moving to an angle of 60° from the vertical is blowing a whistle which has a frequency of 2.0 k Hz. The whistle is 2.0 m from the fixed support point of the swing. A sound detector which detects the whistle sound is kept in front of the swing. The maximum frequency the sound detector detected is
(a) 2.027 kHz
(b) 1.974 kHz
(c) 9.74 kHz
(d) 1.011 kHz
Answer Key:
(a) 2.027 kHz

13. Let $\mathrm{y}=\frac{1}{1+{\mathrm{x}}^2}$ at t = 0 s be the amplitude of the wave propagating in the positive x-direction. At  t = 2 s, the amplitude of the wave propagating becomes  $\mathrm{y}=\frac{1}{1+(\mathrm{x}-2{)}^2}$  Assume that the shape  of the wave does not change during propagation. The velocity of the wave is
(a) 0.5m s^-1  
(b) 1.0m s^-1
(c) 1.5m s^-1  
(d) 2.0m s^-1
Answer Key:
(b) 1.0m s^-1

14. A uniform rope having mass m hangs vertically from a rigid support. A transverse wave pulse is produced at the lower end. Which of the following plots shows the correct variation of speed v with height h from the lower end? 

Answer Key:

15. An organ pipe A closed at one end is allowed to vibrate in its first harmonic and another pipe B open at both ends is allowed to vibrate in its third harmonic. Both A and B are in resonance with a given tuning fork. The ratio of the length of A and B is
(a) $\frac{8}{3}$
(b) $\frac{3}{8}$
(c) $\frac{1}{6}$
(d) $\frac{1}{3}$
Answer Key: 

(c) $\frac{1}{6}$

II. Short Answer Questions

11th physics

III. Long Answer Questions

11th Physics

IV. Exercise

11th Physics