Question #827e8

1 Answer
Apr 20, 2017

4.09 * 10^(-19)J

Explanation:

Use the formula:
E_n = -R_H(1/n^2)
where :
R_H = "Rydberg constant" = 2.18 * 10^(-18)J,
n = "the energy level"

For n = 4:
E_4 = -2.18 * 10^(-18)J(1/4^2) = -1.3625 *10^(-19)J

For n = 2
E_2 = -2.18 * 10^(-18)J(1/2^2) = -5.45 *10^(-19)J

Then to find the energy of the photon, you just calculate the change in energy.

DeltaE = E_"initial" - E_"final"

DeltaE = (-1.3625 *10^(-19)J) - (-5.45 *10^(-19)J)

DeltaE = 4.0875 * 10^(-19)J

Since you only have 3 significant figures, the answer would be:
4.09 * 10^(-19)J