Sunlight falls normally on a surface of area 36 cm2 and exerts an average force of 7.2 × 10-9 N within a time period of 20 minutes. Considering a case of complete absorption the energy - Physics (JEE Main)

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Sunlight falls normally on a surface of area 36 cm2 and exerts an average force of 7.2 × 10-9 N within a time period of 20 minutes. Considering a case of complete absorption the energy flux of incident light is ______.

Options

  • 25.92 × 102 W/cm2  

  • 8.64 × 10-6 W/cm2  

  • 6.0 W/cm2  

  • 0.06 W/cm2  

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Solution

Sunlight falls normally on a surface of area 36 cm2 and exerts an average force of 7.2 × 10-9 N within a time period of 20 minutes. Considering a case of complete absorption the energy flux of incident light is 0.06 W/cm2.

Explanation:

`"I"/"C"xx"area"` = force

⇒ `"I"/"C"xx36xx10^-4 = 7.2 xx 10^-9` 

⇒ I = `(7.2xx10^-9xx3xx10^8)/(36xx10^-9xx10)=(6xx10^-1)/10^-3`

⇒ I = 6 × 102 `"W"/"m"^2` 

⇒ I = 0.06 `"W"/"cm"^2`

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