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Intensity Formula


Intensity is the quantity of energy the wave conveys per unit time across a surface of unit area and it is also equivalent to the energy density multiplied by the wave speed. It is generally measured with units of watts per square meter. Intensity will depend on the strength and amplitude of a wave. Intensity is represented as I. The formula for intensity is articulated by,

Where I is the intensity, P is the power and A is the area of cross section.


Intensity Solved Examples

Let us discuss the questions related to intensity.

Problem 1: Calculate the intensity of a wave whose power is 25KW and the area of cross section is 35×106m2?

Known measures are,
P = 25KW = 25×103×103W, A = 35×106m2×106m2
Intensity formula is,





Problem  2: Calculate the power of a wave whose intensity and area of cross section are 30×10-5W/m2 and 50m2 respectively?

Known quantities are,
I = 30×10-5W/m2 and A = 50m2
Intensity formula is,

P= I x A

P = 30 x 10-5 x 50

= 0.015W