Question

Two identical sinusoidal waves each of amplitude $10mm$ with a phase difference of ${90}^o$ are travelling in the same direction in string. The amplitude of the resultant wave is :

• A. $5mm$
• B. $10\sqrt{2}mm$
• C. $15mm$
• D. $20mm$

Answer 1

Answer: (B)

$10\sqrt{2}mm$

Since the two waves are identical, they have same amplitudes with phase difference of ${90}^o$.
The amplitude of the resultant wave is,
$A=\sqrt{a^2+b^2}=\sqrt{a^2+a^2}=a\sqrt{2}$
Here, $a=10mm,A=10\sqrt{2}mm$