Question

There are two waves having wavelengths $100cm$ and $101cm$ and same velocity $303m/s$. The beat frequency is :

• A. $4Hz$
• B. $1Hz$
• C. $3Hz$
• D. $2Hz$

Answer 1

Answer: (C)

$3Hz$

Key Point If $f_1$ and $f_2$ are the frequencies $(f_1>f_2)$ of the two waves, then the beat frequency $f_b=f_1-f_2$
$f_1=\frac{V_1}{{\lambda }_1}=\frac{303}{100}\times {10}^2=3.03\times {10}^{2}Hz$
For $2nd$ wave, $f_2=\frac{V_1}{{\lambda }_2}=\frac{303}{101}\times {10}^2=3\times {10}^{2}Hz$
So, beat frequency $=f_1-f_2$
$=3.03\times {10}^2-3\times {10}^2=.03\times {10}^2=3Hz$