Download App

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

Rajasthan 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→Rajasthan Board STD 11 Science question papers→Rajasthan Board question paper generator→

Similar questions

A body at rest breaks up into $3$ parts. If $2$ parts having equal masses fly off perpendicularly each after with a velocity of $12m/s$, then the velocity of the third part which has $3$ times mass of each part is
→
A stone is projected from the ground with velocity $25\,m/s$. Two seconds later, it just clears a wall $5 \,m$ high. The angle of projection of the stone is ........ $^o$ $(g = 10m/{\sec ^2})$
→
A ring of mass $m$ is attached to a horizontal spring of spring constant $k$ and natural length $l_0$ . Other end of spring is fixed and ring can slide on a smooth horizontal rod as shown. Now the ring is shifted to position $B$ and released, speed of ring when spring attains it's natural length is
→
Which of the following is an assumption of Kinetic theory of matter?
→
An organ pipe $P_1$ closed at one end vibrating in its first overtone. Another pipe $P_2$ open at both ends is vibrating in its third overtone. They are in a resonance with a given tuning fork. The ratio of the length of $P_1$ to that of $P_2$ is
→
Two small spherical metal balls, having equal masses, are made from materials of densities $\rho_{1}$ and $\rho_{2}\left(\rho_{1}=8 \rho_{2}\right)$ and have radii of $1\; \mathrm{mm}$ and $2\; \mathrm{mm}$, respectively. They are made to fall vertically (from rest) in a viscous medum whose coefficient of viscosity equals $\eta$ and whose denstry is $0.1 \mathrm{\rho}_{2} .$ The ratio of their terminal velocitites would be 
→
The gap between any two rails, each of length $l$ laid on a railway track equal $x$ at $27\,^oC$ . When the temperature rises to $40\,^oC$ , the gap close up. The coefficient of linear expansion of the material of the rail is $\alpha $ . The length $l$ of a rail at $27\,^oC$ will be
→
Eight point masses m that are held in a cubical array by rods of length 1 (whose masses are negligible). Find the moments of inertia of the system about the following axes:
→
Which of the following statements is false for a particle moving in a circle with a constant angular speed
→
A particle of mass $m$ is at rest at the origin at time $t = 0$. It is subjected to a force $F(t) = F_0e^{-bt}$ in the $x$ direction. Its speed $v (t)$ is depicted by which of the following curves?
→