25. SPEED OF LIGHT Speed of Light ( c ) = λf What is the frequency of yellow light, λ = 556nm? f = c / λ = 3 x 10^8 m/s . Convert nm m 556 x 10^-9 m = 5.4 x 10^14 Hz c = 3.00 x 10^8 m/s
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33. What is illumination? E (illumination) = P (luminous flux) 4Пd²(distance) Light Illuminance varies as the inverse square of the distance. Illumination drops off quickly with distance from source.