[kyasarin]

What is the minimum wavelength of a photon of light that can excite an electron in the hydrogen atom from the n=1 to the n=8 energy level?
a) 92.7 nm
b) 122 nm
c) 40.1 nm
d) 60.4 nm
e) 300. nm

First i used ∆E = 2.178 X 10-18 J[1/n2i – 1/n2f], then E = hc/λ
I got 9.459 x 10-9 nm.

[Borek]

[1/n2i – 1/n2f]

I suppose you mean

1/(n_i²) - 1/(n_f²)

I got 9.459 x 10-9 nm.

Show how you've got there, I got one of the answers given.

[kyasarin]

Show how you've got there, I got one of the answers given.

∆E=2.178 X 10-18 J [1/(64) - 1] = 2.1 x 10^-8
e=hc/λ
λ=hc/e=(6.626 x 10^-34 x 2.9979 x 10⁸)/2.1 x 10^-8=
9.459 x 10^-18 m = 9.459 x 10^-9 nm

[ARGOS++]

Dear Kyasarin;

The other way around! – as Mr Borek told you: Index (i) before Index (f).

Let’s start:

deltaE =  2.187 * 10^-18   *   (1/1 – 1/64)  =  2.144 * 10^-18

Now you should get a better result.

Good Luck!
                   ARGOS⁺⁺

[kyasarin]

The other way around! – as Mr Borek told you: Index (i) before Index (f).

Let's start:

deltaE =  2.187 * 10^-18   *   (1/1 – 1/64)  =  2.144 * 10^-18

my book says to use -2.187 x 10-18 J (1/n_f²-1/n_i²) & you say to use 2.187 x 10-18 J (1/n_i²-1/n_f²) which are essentially the same equation.

deltaE =  2.187 * 10^-18  *   (1/1 – 1/64)  =  2.144 * 10^-18

i just got the same answer using my book's formula, i must have copied the answer wrong from the calculator. (10^-18 vs. 10^-8) wow i feel stupid. 

I just got A) 92.7 nm, so i hope that's the right answer.

thanks for everyone's help 

[ARGOS++]

Dear Kyasarin;

Now it’s quite easy to agree with you(r result).

Good Luck!
                   ARGOS⁺⁺