The correct answer is:
<span>The rate at which a waves energy flows through a given unit of area
In fact, light intensity is defined as the light power per unit of area:
</span>
<span>but the power is the energy carried by the light per unit of time:
</span>
<span>this means that the intensity can be rewritten as
</span>
<span>
So, it's basically the rate of energy (per unit of time) through a given surface.</span>
<span>The rate at which a waves energy flows through a given unit of area
In fact, light intensity is defined as the light power per unit of area:
</span>
<span>but the power is the energy carried by the light per unit of time:
</span>
<span>this means that the intensity can be rewritten as
</span>
So, it's basically the rate of energy (per unit of time) through a given surface.</span>