Chemistry question pls solve

Dear student

E = \frac{h c}{λ} = \frac{6.626 \times 10^{- 34} \times 3 \times 10^{8}}{400 \times 10^{- 9}} = \frac{4.969 \times 10^{- 19}}{1} N o . o f p h o t o n s e m i t t e d p e r s e c o n d = \frac{100}{4.969 \times 10^{- 19}} = 2 \times 10^{20} p h o t o n s p e r s e c o n d

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