Tag: time period, frequency and amplitude of sound

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Questions Related to time period, frequency and amplitude of sound

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

The wavelength of light absorbed by $Pr$ form of phytochrome is:-

  1. $620 nm$

  2. $640 nm$

  3. $680 nm$

  4. $720 nm$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Pr form absorbs light between $660$ to $680 nm$ and absorbs at a peak of $666 nm$. It is the form synthesized in dark-grown seedlings. When Pr absorbs red light, it is converted to the $Pfr$ form.

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

The frequency of a man's voice is $300Hz$ and its wavelength is $1$ meter. If the wavelength of a child's voice is $1.5m$, then the frequency of the child's voice is:

  1. $200Hz$

  2. $150Hz$

  3. $400Hz$

  4. $350Hz$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

We know that ,

$f=\dfrac{c}{\lambda}$
So,
$\dfrac{f _{man's voice}}{f _{child's voice}}=\dfrac{\dfrac{c}{\lambda _{man's voice}}}{\dfrac{c}{\lambda _{child's voice}}}$
$\dfrac{f _{man's voice}}{f _{child's voice}}$=$\dfrac{\lambda _{child's voice}}{\lambda _{man's voice}}$     
$\dfrac{300}{f _{child's voice}}=\dfrac{1.5}{1}$
$f _{child's voice}=\dfrac{300}{1.5}$
$f _{child's voice}=200 Hz$
  

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

two waves of same frequency and of intensity ${I} _{0}$ and $9{I} _{0}$ produces interference. If at a certain point the resultant intensity is $7{I} _{0}$ then the minimum phase difference between the two sound waves will be

  1. ${90}^{0}$

  2. ${150}^{0}$

  3. ${120}^{0}$

  4. ${100}^{0}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$\begin{array}{l} 7{ I _{ o } }={ I _{ o } }+a{ I _{ o } }+2\sqrt { { I _{ o } } } \sqrt { x{ I _{ o } } } \cos  \Delta \phi  \ \Rightarrow 7{ I _{ o } }=10{ I _{ o } }+6\cos  \Delta \phi  \ \Rightarrow -3{ I _{ o } }=6\cos  \Delta \phi  \ \cos  \Delta \phi ={ { -1 } }{ 2 } \ \Delta \phi =\dfrac { { 2\pi  } }{ 3 } =\dfrac { { 2\times 180 } }{ 3 } ={ 120^{ 0 } } \ Hence, \ option\, \, C\, \, is\, \, correct\, \, answer. \end{array}$

Multiple choice physics world of sounds characteristics of sound wave time period, frequency and amplitude of sound sound waves are longitudinal waves

When you speak to your friend which of the following quantities have a unique value in the sound produced by both the boys?

  1. amplitude

  2. wave velocity

  3. frequency

  4. wavelength
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Out of the given quantities , wave velocity has a unique value . Because both the friends are producing the sound in the same medium , and wave velocity depends upon medium , which is not changing here .

Amplitude of the sounds depends upon the energy given by any of the friends to sound , so it may change .
Frequency of sound depends upon the thickness of vocal cords of two friends , so it also may vary . Now wavelength $\lambda \propto 1/f$, for a constant velocity , when frequency $f$ changes , wavelength will also change .