# 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)$3.5 \times 10 ^ { -6} Ns$

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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