1.

An isotropic point source emits light with wavelength 500 nm. The radiation power of source is P = 10 W. Find the number of photons passing through unit area per second at a distance of 3 m from the source.

A. 5.92 × 1017/m2 s
B. 2.23 × 1017/m2 s
C. 2.23 × 1018/m2 s
D. 5.92 × 1018/m2 s
Answer» C. 2.23 × 1018/m2 s


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