Given data:
* The illuminance of an object is 1.5 m.
* The luminous flux is 665 lumens.
Solution:
The illuminance in terms of the flux and distance is,
[tex]E=\frac{P}{4\pi\times d^2}[/tex]where P is the flux, and d is the distance of the object,
Substituting the known values,
[tex]E=\frac{665}{4\times\pi\times(1.5)^2}[/tex]By solving the above values,
[tex]E=23.5\text{ Ix}[/tex]Thus, the illuminance is 23.5 Ix.
Hence, 3rd option is the correct answer.
