Question

When two waves of almost equal frequencies ${\upsilon }_1$ and ${\upsilon }_2$ reach at point simultaneously, the time interval between successive maxima is

• A. ${\upsilon }_1+{\upsilon }_2$
• B. ${\upsilon }_1-{\upsilon }_2$
• C. $\frac{1}{{\upsilon }_1+{\upsilon }_2}$
• D. $\frac{1}{{\upsilon }_1-{\upsilon }_2}$

Answer 1

Answer: (D)

$\frac{1}{{\upsilon }_1-{\upsilon }_2}$

When two waves of almost equal frequencies ${\upsilon }_1$ and ${\upsilon }_2$ reach at a point simultaneously, beats are produced.
Beat frequency, ${\upsilon }_{beat}={\upsilon }_1-{\upsilon }_2$
Time interval between successive maxima
$=\frac{1}{{\upsilon }_{beat}}=\frac{1}{{\upsilon }_1-{\upsilon }_2}$