Light is incident normally on a completely absorbing surface with an energy flux of  25 Wcm ^{-2} . If the surface has an area of 25cm ^{-2} ,The momentum transferred to the surface in 40 min time duration will be : 

 

  • Option 1)

    6.3 \times 10 ^ { -4} Ns

  • Option 2)

    1.4 \times 10 ^ { -6} Ns

  • Option 3)

    5.0 \times 10 ^ { -3} Ns

  • Option 4)

    3.5 \times 10 ^ { -6} Ns

Answers (1)

Pressure = I/C 

Force = Pressure * Area = I/C * A 

momentum transferred =

 F \cdot \Delta T \\\\ = \frac{I}{C} \cdot A \cdot \Delta T \\\\ = \frac{25 \times 10 ^ 4 }{3 \times 10 ^8 }\times 25 \times 10 ^{-4} \times 40 \times 60 \\\\ = 5 \times 10 ^{-3}Ns


Option 1)

6.3 \times 10 ^ { -4} Ns

Option 2)

1.4 \times 10 ^ { -6} Ns

Option 3)

5.0 \times 10 ^ { -3} Ns

Option 4)

3.5 \times 10 ^ { -6} Ns

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