Question

$( - 20) \times ( - 10)$
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Answer 1

Answer:

— × – = +

-20 ×-10 = 200

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Answer 2

ANSWER

We know that , Power = (Number of photons per second ) × λhC 

200 = 4×1020×λ2×10−25

∴λ = 4×10−7 m