Figure shows a small diffused plane source S placed over a horizontal table-top at a distance of 2.4 m with its plane parallel to the table-top. The illuminance at the point A directly below the source is 25 lux. Find the illuminance at a point B of the table at a distance of 1.8 m from A.
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Solution

Let x be the distance moved.
Let the illuminance of the candle and the lamp at a distance 1 m be I_C and I_L respectively. According to question,

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Figure shows a small diffused plane source S placed over a horizontal table-top at a distance of 2.4 m with its plane parallel to the table-top. The illuminance at the point A directly below the source is 25 lux. Find the illuminance at a point B of the table at a distance of 1.8 m from A. Figure

Let x be the distance moved. Let the illuminance of the candle and the lamp at a distance 1 m be IC and IL respectively. According to question,

Figure shows a small diffused plane source S placed over a horizontal table-top at a distance of 2.4 m with its plane parallel to the table-top. The illuminance at the point A directly below the source is 25 lux. Find the illuminance at a point B of the table at a distance of 1.8 m from A.
Figure

Let x be the distance moved.
Let the illuminance of the candle and the lamp at a distance 1 m be I_C and I_L respectively. According to question,