91Ó°ÊÓ

The electric field amplitude of the first wave is $A_1=10\mathrm{μ³Õ}/\mathrm{m}$.

The electric field amplitude of the second wave is role="math" localid="1663147301551" $A_2=5\mathrm{μ³Õ}/\mathrm{m}$.

The electric field amplitude of the third wave is role="math" localid="1663147316555" $A_3=5\mathrm{μ³Õ}/\mathrm{m}$.

The phase angle between first and second wave is ${\mathrm{ϕ}}_1=45°$.

The phase angle between second and third wave is ${\mathrm{ϕ}}_2=90°$.

The phase angle between first and third wave is ${\mathrm{ϕ}}_3=45°$.

The amplitude of the resultant wave is equal to the vector sum of the amplitude of each wave.

The resultant amplitude of all wavesat point P is given as:

$E_r=\sqrt{A_1^2+A_2^2+A_3^2+2A_1{A}_2\cos {\mathrm{Ï•}}_1+2A_2{A}_3\cos {\mathrm{Ï•}}_2+2A_3{A}_1\cos {\mathrm{Ï•}}_3}$

Substitute all the values in equation.

Hence, the resultant amplitude of all waves at point P is $17.1\mathrm{μ³Õ}/\mathrm{m}$.