Question

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:

• A. $200Hz$
• B. $150Hz$
• C. $400Hz$
• D. $350Hz$

Answer 1

The correct option is A $200Hz$

We know that ,

$f=\frac{c}{\lambda }$

So,

$\frac{f_{ma{n}^{\prime }svoice}}{f_{chil{d}^{\prime }svoice}}=\frac{\frac{c}{{\lambda }_{ma{n}^{\prime }svoice}}}{\frac{c}{{\lambda }_{chil{d}^{\prime }svoice}}}$

$\frac{f_{ma{n}^{\prime }svoice}}{f_{chil{d}^{\prime }svoice}}$=$\frac{{\lambda }_{chil{d}^{\prime }svoice}}{{\lambda }_{ma{n}^{\prime }svoice}}$

$\frac{300}{f_{chil{d}^{\prime }svoice}}=\frac{1.5}{1}$

$f_{chil{d}^{\prime }svoice}=\frac{300}{1.5}$

$f_{chil{d}^{\prime }svoice}=200Hz$