Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Waves question

2018 · Q154
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /NEET
  3. /Physics
  4. /Waves
  5. /2018 · Q154

Waves question

2018 · Q154

NEETPhysicsWavesMCQ+4 / −1
The fundamental frequency in an open organ pipe is equal to the third harmonic of a closed organ pipe. If the length of the closed organ pipe is 20 cm, the length of the open organ pipe is
  1. A
    13.2 cm
  2. B
    8 cm
  3. C
    12.5 cm
  4. D
    16 cm
View written solutionFree

Correct answer: A

For closed organ pipe, third harmonic

n = (2N−1)V4l=3V4l{{\left( {2N - 1} \right)V} \over {4l}} = {{3V} \over {4l}}4l(2N−1)V​=4l3V​ (∵\because∵ N = 2 )

For open organ pipe, fundamental frequenty

n = NV2l=V2l′{{NV} \over {2l}} = {V \over {2l'}}2lNV​=2l′V​ (∵\because∵ N = 1 )

Given, third harmonic for closed organ pipe = fundamental frequency for open organ pipe.

∴\therefore∴ 3V4l=V2l′{{3V} \over {4l}} = {V \over {2l'}}4l3V​=2l′V​

⇒\Rightarrow⇒ l' = 4l3×2{{4l} \over {3 \times 2}}3×24l​ = 2l3{{2l} \over 3}32l​ = 2×203{{2 \times 20} \over 3}32×20​ = 13.33 cm

PreviousNext

More from Waves

  • A tuning fork is used to produce resonance in a glass tube. The length of the air column in this tube can be adjusted by a variable piston. At room temperature of 27°C two successive resonances are produced at 20 cm and 73 cm of column…2018 · MCQ
  • The two nearest harmonics of a tube closed at one end and open at other end are 220 Hz and 260 Hz. What is the fundamental frequency of the system ?2017 · MCQ
  • An air column, closed at one end open at the other, resonates with a tuning fork when the smallest length of the column is 50 cm. The next larger length of the column resonating with the same tuning fork is2016 · MCQ
  • A uniform rope of length L and mass m1 hangs vertically from a rigid support. A block of mass m2 is attached to the free end of the rope. A transverse pulse of wavelength λ1 is produced at the lower end of the rope. The wavelength…2016 · MCQ
  • The second overtone of an open organ pipe has the same frquency as the first overtone of a closed pipe L metre long. The length of the open pipe will be2016 · MCQ
  • Three sound waves of equal amplitudes have frequencies (n − 1), n, (n + 1). They superimpose to give beats. The number of beats produced per second will be2016 · MCQ
  • A string is stretched between fixed points separated by 75.0 cm. It is observed to have resonant frequencies of 420 Hz and 315 Hz. There are no other resonant frequencies between these two. The lowest resonant frequency for this string is2015 · MCQ
  • 4.0 g of a gas occupies 22.4 litres at NTP. The specific heat capacity of the gas at constant volume is 5.0 J K−1 mol−1. If the speed of sound in this gas at NTP is 952 m s−1, then the heat capacity at constant pressure is (Take gas…2015 · MCQ