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STD 12 - 9. Ray optics abd optical instruments — NEET STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceNEETSTD 12 - 9. Ray optics abd optical instruments4 Marks
Question
A point source of light moves in a straight line parallel to a plane table. Consider a small portion of the table directly below the line of movement of the source. The illuminance at this portion varies with its distance $r$ from the source as
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Answer

(c) $I = \frac{{Lh}}{{{r^3}}}$

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