Question

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

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

Answer 1

4)

Explanation:

`f = c/lamda`
`E=hf`

Remember unit conversion we're using nm so it's `* 10^-9`
so let's get f:

- `*` is the same as x I.E Multiplied by
- remember `c = 3 * 10^8 ms^-1`

`f = (3 * 10^8)/(650 * 10^-9)` which = `4.6 * 10^14`

• We want E
• We have h as it's a constant: `6.63 * 10^-34`

`E = (6.63 * 10^-34)(4.6 * 10^14)`
which gives `3.04 * 10^-19`

Which is about 4)