Sound Waves and Beats - Class XI Physics
Covers sound wave fundamentals and practical applications of beats including beat frequency calculations, Doppler effect beats, and musical applications
Questions
What happens when two sound waves of frequencies differing by more than 10 Hz reach our ear simultaneously?
- beats are not produced
- the waves destroy each other's effect
- interference of sound does not take place.
- beats are produced but cannot be heard
You are listening to an $A$ note played on a violin string. Let the subscript $s$ refer to the violin string and $a$ refer to the air. Then:
- $f _{s}=f _{a}$ but $\lambda _{s}\neq\lambda _{a}$
- $f _{s}=f _{a}$ and $\lambda _{s}=\lambda _{a}$
- $\lambda _{s}=\lambda _{a}$ but $f _{s}\neq f _{a}$
- $\lambda _{s}\neq\lambda _{a}$ and $f _{s}\neq f _{a}$
The fundamental frequency of a sitar wire is 440 vibrations per seond. If the sitar player reduces the length of the wire by $1/5^{th}$, then the change in the frequency of sitater wire will be
- 2200 vibrations/sec
- 1760 vibrations/sec
- 440 vibrations/sec
- 110 vibrations/sec
A source of sound of frequency 256 Hz is moving towards a wall with a velocity of 5 m/s. The number of beats per second heard by a stationary observer between the source and the wall is (Velocity of sound = 330 m/s)
- 8
- 3
- 5
- 2
Two waves $\mathrm{y} _{1}=\mathrm{A}\cos(0.5\pi \mathrm{x}-100\pi \mathrm{t})$
and $\mathrm{y} _{2}=\mathrm{A}\cos(0.46\pi \mathrm{x}-92\pi \mathrm{t})$ are travelling in a pipe placed along $\mathrm{x}$-axis. Find the number of times intensity is maximum in time interval of 1 sec.
- 4
- 6
- 8
- 10
The musical interval between tube two tine of frequency $400\ Hz$ and $200\ Hz$ is:
- $2$
- $200$
- $1$
- $none\ of\ these$
The characteristics of sound with the help of which we can distinguish between a SHRILL note and a GRAVE note is
- Loudness
- Pitch
- Quality
- Intensity
Beats are heard at the rate of $12$ every $5$ seconds when two open organ pipes of lengths $84\ cm$ and $85\ cm$ are sounded together in their fundamental modes. Find the velocity of sound in air. (An open organ pipe has an antinode at each end.
- $342.7\ m/s$.
- $300.7\ m/s$.
- $350.7\ m/s$.
- $400.7\ m/s$.
An under water swimmer sends a sound signal to the surface. It is produces 5 betas/sec when compared with fundamental tone of a pipe of $20$ cm length closed at one end what is wavelength of sound in water. (take V water=$1500 m/sec$ Vair=$360 m/sec$)
- $3.3 m$ or $3.37 m$
- $4.4 m$ or $4.47 m $
- $2.5 m$ or $2.7 m$
- $1 m$ or $1.7 m$