Which of the following energy transitions for electrons will occur when red light (650 nm) is absorbed by an atom?

Question

1) 3.4 x 10-36 J
2) 4.3 x 10-31 J
3) 4.6 x 105 J
4) 3.0 x 10-19 J

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Answer 1 · 2017-10-20T16:41:04

4)

$f = \frac{c}{λ}$ $f = c/lamda$
$E = h f$ $E=hf$

Remember unit conversion we're using nm so it's $\cdot 10^{- 9}$ $* 10^-9$
so let's get f:

- $\cdot$ $*$ is the same as x I.E Multiplied by
- remember $c = 3 \cdot 10^{8} m s^{- 1}$ $c = 3 * 10^8 ms^-1$

$f = \frac{3 \cdot 10^{8}}{650 \cdot 10^{- 9}}$ $f = (3 * 10^8)/(650 * 10^-9)$ which = $4.6 \cdot 10^{14}$ $4.6 * 10^14$

$E = (6.63 \cdot 10^{- 34}) (4.6 \cdot 10^{14})$ $E = (6.63 * 10^-34)(4.6 * 10^14)$
which gives $3.04 \cdot 10^{- 19}$ $3.04 * 10^-19$

Which is about 4)