Download App

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

Gujarat BoardEnglish MediumSTD 11 SciencePhysics14. waves and sound1 Mark
MCQ
The equation of a wave disturbance is given as : $y = 0.02 cos \left( {\frac{\pi }{2} + 50\pi t} \right) cos (10 x),$ where $x$ and $y$ are in meters and $t$ in seconds. Choose the wrong statement:
  • A
    Antinode occurs at $x = 0.3 \,\,m$
  • B
    The wavelength is $ 0.2\,\, m$
  • ✓
    The speed of the constituent waves is $4\,\, m/s$
  • D
    Node occurs at $x = 0.15\,\, m$
✓

Answer

Correct option: C.
The speed of the constituent waves is $4\,\, m/s$
c
$y=0.02 \cos (\pi / 2+50 \pi \times t) \cos (10 \pi \times x)$

At $x=0.3\,m$

$y=0.02 \cos (\pi / 2+50 \pi \times t) \cos (3 \pi)=-0.02 \cos (\pi / 2+50 \pi \times t)$ (It is

right)

Now compare the given equation by the standard stationary wave equation,

$y=A \cos (\phi+\omega \times t) \cos (2 \pi \lambda \times x)$

$2 \pi \lambda=10 \pi, \lambda=0.2\,m$ (it is also right)

$\text { At } x=0.15\,m$

$y=0.02 \cos (\pi / 2+50 \pi \times t) \cos (\pi / 2)$

and

$v = A \omega=0.02 * 50 \pi=\pi ms ^{-1}$

Hence, option " $C$ " is wrong.

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 particle of mass $10\, gm$ is describing $S.H.M.$ along a straight line with period of $2\, sec$ and amplitude of $10, cm$. Its kinetic energy when it is at $5 \,cm$ from its equilibrium position is
→
A ball of mass $0.25\, kg$ attached to the end of a string of length $1.96 \,m$ is moving in a horizontal circle. The string will break if the tension is more than $25 \,N$. ..........  $m/s$ is the maximum speed with which the ball can be moved
→
On a windless day, sound emanate isotropically from a point source. Rays of the sound waves emanated from a point source placed close to ground are shown in the figure. Consider horizontal wind towards the left blowing with constant velocity, which is uniform everywhere. In the following figures, rays of sound waves in presence of the wind are shown. Which one is the most correct representation?
→
A tube-well pumps out $2400\; kg$ of water per minute. If water is coming out with a velocity of $3 \;ms ^{-1}$. How much work is done, if the pump runs for $10\; hours$?
→
A body of mass $400g$ connected to a spring with spring constant $10Nm^{-1}$, executes simple harmonic motion, time period of oscillation is
→
A vector in $x-y$ plane makes an angle of $30^{\circ}$ with $y$-axis The magnitude of $y$-component of vector is $2 \sqrt{3}$. The magnitude of $x$-component of the vector will be
→
A perpendicular material is place in a magnetic fields. Consider the following statemetns:
  1. If the magnetic field is increased, the magnetization is increased.
  2. If the temperature is increased, the magnetization is increased.
→
It is possible to recognise a person by hearing his voice even if he is hidden behind a wall. This is due to the fact that his voice
→
Four spheres $A, B, C$ and $D$ are of same radius but made of different metals. Their densities are in ratio $6 : 3 : 4 : 5$ and specific heats are in ratio $2 : 5 : 4 : 6$ . These are initially kept at the same temperature and placed in the same surroundings. The sphere which has the slowest rate of cooling is
→
Water flows out of the hole on the side of a bucket and follows a parabolic path. If the bucket falls freely under gravity, ignoring air resistance, the water flow
→