Download App

14. waves and sound — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
A tuning fork vibrating with a sonometer having $20\,cm$ wire produces $5$ beats per sec. The beat frequency does not change if the length of the wire is changed to $21\,cm$. The frequency of the tuning fork must be ..... $Hz$
  • A
    $200$
  • B
    $210$
  • ✓
    $205$
  • D
    $215$
✓

Answer

Correct option: C.
$205$
c
The frequency of vibrations of a sonometer wire is given by :

$\mathrm{n}=\frac{1}{2 \mathrm{L}} \sqrt{\frac{\mathrm{T}}{\mathrm{m}}}$

The tuning fork produces $5$ beats per second with lengths $20 \mathrm{\,cm}$ and $21 \mathrm{\,cm}$. If $\mathrm{n}$ be frequency of fork, then

$\mathrm{n}+5=\frac{1}{2 \times 0.20} \sqrt{\frac{\mathrm{T}}{\mathrm{m}}}$          .........$(i)$

$\mathrm{n}-5=\frac{1}{2 \times 0.21} \sqrt{\frac{\mathrm{T}}{\mathrm{m}}}$           .........$(ii)$

Dividing eqn. $(i)$ by $(ii)$ we get:

hence, $\quad \frac{n+5}{n-5}=\frac{0.21}{0.20}$

or  $0.2 n+1=0.21 n-1.05$

or  $1+1.05=0.21 n-0.2 n^{\prime}$

or  $0.05=0.01\, n$

or  $\mathrm{n}=205 \mathrm{\,Hz}$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

More "M.C.Q (1 Marks)" from 14. waves and sound→14. waves and sound — all question types→Physics STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

A body of mass $1\ kg$ is thrown with a velocity of $10\ ms^{-1}$ at an angle of $60^\circ$ with the horizontal. Its momentum at the highest point is:
→
A physical quantity $\vec{S}$ is defined as $\vec{S}=(\vec{E} \times \vec{B}) / \mu_0$, where $\vec{E}$ is electric field, $\vec{B}$ is magnetic field and $\mu_0$ is the permeability of free space. The dimensions of $\vec{S}$ are the same as the dimensions of which of the following quantity (ies)?

$(A)$ $\frac{\text { Energy }}{\text { charge } \times \text { current }}$

$(B)$ $\frac{\text { Force }}{\text { Length } \times \text { Time }}$

$(C)$ $\frac{\text { Energy }}{\text { Volume }}$

$(D)$ $\frac{\text { Power }}{\text { Area }}$

→
The displacement of a particle executing $SHM$ is given by $y=0.25 \sin 200 t$ $cm$. The maximum speed of the particle is $.........cm s^{-1}$
→
One mole of an ideal monoatomic gas is compressed isothermally in a rigid vessel to double its pressure at room temperature, $27\,^oC$.The work done on the gas will be
→
A body of mass $10 kg$ is projected at an angle of $45^{\circ}$ with the horizontal. The trajectory of the body is observed to pass through a point $(20,10)$. If $T$ is the time of flight, then its momentum vector, at time $t =\frac{ T }{\sqrt{2}}$, is.

$\left[\right.$ Take $\left.g=10 m / s ^{2}\right]$

→
The two vectors have magnitudes $3$ and $5$. If angle between them is $60^o$, then the dot product of two vectors will be
→
The bulk modulus of rubber is $9.1\times 10^8\,N/m^2$. To ......... $m$ depth a rubber ball be taken in a lake so that its volume is decreased by $0.1\,\%$ .
→
The length, breadth and thickness of a block are given by $l = 12\,cm,\,b = 6\,cm$ and $t = 2.45\,cm$ The volume of the block according to the idea of significant figures should be
→
At about $4^\circ C,$ a certain amount of water has maximum:
→
The vertical limbs of a $U$ shaped tube are filled with a liquid of density $\rho$ upto a height $h$ on each side. The horizontal portion of the $U$ tube having length $2h$ contains a liquid of density $2\rho$ . The $U$ tube is moved horizontally with an accelerator $g/2$ parallel to the horizontal arm. The difference in heights in liquid levels in the two vertical limbs, at steady state will be 
→