Download App

Model Paper 7 — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysicsModel Paper 71 Mark
MCQ
A point source emits sound equally in all directions in a non-absorbing medium. Two points P and Qare at distances of 2 m and 3 m respectively from the source. The ratio of the intensities of the waves at P and Q is:
  • A
    $4: 9$
  • B
    $2: 3$
  • C
    $3: 2$
  • D
    $9: 4$
✓

Answer

(d) $9: 4$
Explanation: Intensity $=\frac{\text { energy }}{\text { time } \times \text { area }}=\frac{\text { power }}{\text { area }}$
From a point source, energy spreads over the surface of a sphere of radius $r$.
$\therefore$ Intensity, $I =\frac{P}{A}=\frac{P}{4 \pi r^2}$
or $I \propto \frac{1}{r^2}$
$
\frac{I_1}{I_2}=\left(\frac{r_2}{r_1}\right)^2=\left(\frac{3}{2}\right)^2=\frac{9}{4}
$

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 Model Paper 7→Model Paper 7 — all question types→Physics STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

Initial pressure and volume of a gas are $ P$ and $V$ respectively. First it is expanded isothermally to volume $4V$ and then compressed adiabatically to volume $ V$. The final pressure of gas will be
→
The temperature of a gas is $ -68^\circ C$. At ...... $^oC$ temperature will the average kinetic energy of its molecules be twice that of at $ -68^\circ C$
→
Two sound waves of wavelengths $5m$ and $6m$ formed $30$ beats in $3$ seconds. The velocity of sound is  .... $ms^{-1}$
→
A system changes from the state $({P_1},\;{V_1})$ to $({P_2},{V_2})$ as shown in the figure. What is the work done by the system
→
If two liquids of same volume but different densities $\rho_1$ and $\rho_2$ are mixed, then density of mixture is given by:
→
The r.m.s. velocity of a gas at a certain temperature is $\sqrt 2 $ times than that of the oxygen molecules at that temperature. The gas can be
→
A rocket is fired upward from the earth's surface such that it creates an acceleration of $19.6 \,m/sec^2$. If after $5 \,sec$ its engine is switched off, the maximum height of the rocket from earth's surface would be.........$m$
→
A wooden wedge of mass $M$ and inclination angle $(\alpha)$ rest on a smooth floor. A block of mass $m$ is kept on wedge. A force $F$ is applied on the wedge as shown in the figure such that block remains stationary with respect to wedge. So, magnitude of force $F$ is
→
A hollow spherical ball of uniform density rolls up a curved surface with an initial velocity $3\, m / s$ (as shown in figure). Maximum height with respect to the initial position covered by it will be $...........cm$.
→
Which of the following quantities is zero on an average for the molecules of an ideal gas in equilibrium?
→