Specific heat of water is `4.2 J//g.^(@)C`. If light of frequency `3 xx 10^(29)Hz` is used to heat 400 g of water from `20^(@)C` to `40^(@)C`, the number of moles of photons needed will be
A
`1.69 xx 10^(29) `
B
`1.69 xx 10^(28) `
C
`2.80 xx 10^(4) `
D
`2.80 xx 10^(5)`
Text Solution
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The correct Answer is:
B
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