[11.1.10.1] The effective intensity Ie of a flashing light is, conventionally:

I_{e}= I _{o} t/(t+0.2)

for a source of constant magnitude I0 over time duration t.

For a time-varying source I(t), expressed in candelas:

I_{e}= \frac{\int_{t_{1}}^{t_{2}} I(t) dt}{(t_{2} - t_{1}) + 0.2}

The items t1 and t2 are so chosen as to maximize the calculated effective intensity. It is then found that the actual intensity It at time t1 or t2 is equal to the calculated equivalent intensity Ie.

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