Fa.ara
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#1
Report Thread starter 3 years ago
#1
HI, can some help me with this question
https://postimg.cc/6ThKLt0b
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username3249896
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#2
Report 3 years ago
#2
Inverse square law means relative light intensity is inversely proportional to square of distance
 \displaystyle I \alpha \dfrac{1}{d^2}
hence
 I = \dfrac{k}{d^2}

If distance doubles, light intensity is multiplied by factor 1/4
If distance halves, light intensity is multiplied by 4


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Method 1:
Calculate the constant k by using
 k = Id^2
Replace light intensities and calculate distance
Replace distance and calculate light intensity

Method 2:
Since  I = \dfrac{k}{d^2}
 Id^2 is a constant
hence
 I_1d_1^2 = I_2d_2^2
hence replace one pair of known values of intensity and distance
replace one light intensity and calculate unknown distance
replace one distance and caluclate unknown light intensity
Last edited by username3249896; 3 years ago
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