# Intensity Formula

The intensity of a wave measures the power passing through a surface unit perpendicular to the direction of propagation of the wave.

Intensity = power/ surface perpendicular to the direction of propagation

The equation is written

I = P/S

We have:

I = Intensity

P = power

S = surface perpendicular to the direction of propagation

Intensity Questions:

1) Calculate the intensity of a wave whose power is 36kW and the area of cross section is 45km^{2}.

Answer: First calculate the intensity using the formula above, where P = 36kW and S = 45km^{2}

I = P/S

I = 36*10^{3}W/45*10^{6}m^{2}

I = 0,8*10^{3}W/m^{2}.

2) Calculate the power of a wave whose intensity is 40x10^{-4} W/m ^{2} and cross section area is 800m^{2}.

Answer: First calculate the power by clearing P of the formula above, where I = 40x10^{-4} W/m^{2}and S = 800m^{2}

I = P/S

P = I*S

P = 40x10^{-4} W/m^{2}* 800m^{2}

P = 3.2W.

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