Specific heat of water is 4.2 ,J / g ^{circ} | vedclass

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Question

(b)

$S=4.231 g ^{\circ} C$

$v=3 	imes 10^9 \,Hz$

$m=400 \,g$

Energy of one photon $=h v$

Heat needed for $20^{\circ} C$ temp. change $

Vedclass · Accepted Answer

$1.69 	imes 10^{28}$

Vedclass · Answer

(b)

$S=4.231 g ^{\circ} C$

$v=3 	imes 10^9 \,Hz$

$m=400 \,g$

Energy of one photon $=h v$

Heat needed for $20^{\circ} C$ temp. change $=m s \Delta T=400 	imes 4.2 	imes 20 \,J$

$	herefore$ Number of photons $=\frac{400 	imes 4.2 	imes 20}{h v}=\frac{400 	imes 4.2 	imes 20}{6.63 	imes 10^{-34} 	imes 3 	imes 10^9}=1689 	imes 10^{25}=1.69 	imes 10^{28}$

Specific heat of water is $4.2 \,J / g ^{\circ} C$. If light of frequency $3 \times 10^9 \,Hz$ is used to heat $400 \,gm$ of water from $20^{\circ} C$ to $40^{\circ} C$, the number of photons needed will be

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