$\"\"$

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Flicker first disappears is given by $\"\"$ ,

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Where

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$\"\"$ : Minimum frequency.

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$\"\"$ : The intensity of the light from the screen that reaches the viewer.

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$\"\"$ : Constant of proportionality.

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a.

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The intensity of the light perceived by a moviegoer $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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The quotient property of logarithm : $\"\"$ .

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$\"\"$

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The power property of logarithm : $\"\"$ .

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$\"\"$ .

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$\"\"$

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b.

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Find move affect the value of $\"\"$ .

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Let $\"\"$ be the minimum frequency at a distance $\"\"$ .

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$\"\"$

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Let $\"\"$ be the minimum frequency a distance $\"\"$ .

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$\"\"$

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Apply product property of logarithm : $\"\"$ .

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$\"\"$

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Move affect to the value of $\"\"$ is $\"\"$ .

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$\"\"$

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Cancel common terms.

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$\"\"$

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Apply power property of logarithm : $\"\"$ .

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$\"\"$

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Move affect the value of $\"\"$ is $\"\"$ .

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$\"\"$

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a. $\"\"$

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b. Move affect the value of $\"\"$ is $\"\"$ .