A tuning fork of frequency 392 Hz, resonates with 50 cm length of… - Vidyadip

MCQ

A tuning fork of frequency $392 Hz,$ resonates with $50 cm $ length of a string under tension ($T$). If length of the string is decreased by $2\%$, keeping the tension constant, the number of beats heard when the string and the tuning fork made to vibrate simultaneously is

A
$4$
B
$6$
✓
$8$
D
$12$

✓

Answer

Correct option: C.

$8$

c
(c) $n \propto \frac{1}{l}$ ==> $\frac{{\Delta n}}{n} = - \frac{{\Delta l}}{l}$

If length is decreased by $2\%$ then frequency increases by $2\%$ i.e., $\frac{{{n_2} - {n_1}}}{{{n_1}}} = \frac{2}{{100}}$

==> ${n_2} - {n_1} = \frac{2}{{100}} \times {n_1} = \frac{2}{{100}} \times 392 = 7.8 \approx 8.$

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

The dimensions of thermal resistance are

One main scale division of a vernier callipers is $a$ $cm$ and $n ^{\text {th }}$ division of the vernier scale coincide with $( n -1)^{\text {th }}$ division of the main scale. The least count of the callipers in $mm$ is

Assuming the earth to be a sphere of uniform mass density, a body weighed $300 \mathrm{~N}$ on the surface of earth. How much it would weigh at $R / 4$ depth under surface of earth?

A polyatomic gas with six degrees of freedom does $25\,\,J$ of work when it is expanded at constant pressure. The heat given to the gas is ..... $J$

A wave represented by the equation ${y_1} = a\,\cos \,\left( {kx - \omega t} \right)$ is superimposed with another wave to form a stationary wave such that the point $x = 0$ is node. The equation for the other wave is

If $g \propto \frac{1}{{{R^3}}}$ (instead of $\frac{1}{{{R^2}}}),$ then the relation between time period of a satellite near earth's surface and radius $R$ will be

A horizontal bridge is built across a river. A student standing on the bridge throws a small ball vertically upwards with a velocity $4\,m s ^{-1}$. The ball strikes the water surface after $4\,s$. The height of bridge above water surface is $......\,m$ $\left(\right.$ Take $\left.g=10\,m s ^{-2}\right)$

Two waves of equal amplitude $A$ and equal frequency travel in the same direction in a medium. The amplitude of the resultant wave is:

Which of the following is best close to an ideal black body

The temperature of argon, kept in a vessel, is raised by $1^\circ C$ at a constant volume. The total heat supplied to the gas is a combination of translational and rotational energies. Their respective shares are