Question

Rank from longest to shortest wavelength?

Place the following transitions of the hydrogen atom in order from longest to shortest wavelength of the photon emitted.

n=7 to n=4
n=5 to n=3
n=4 to n=2
n=3 to n=2

Answer 1

`bb"D"color(white)(l)(7 → 4) > bb"C"color(white)(l)(5 →3) > bb"B"color(white)(l)(3 → 2) >bb"A"color(white)(l)(4 → 2)`

Explanation:

The electrons that fall to the (`n=2`) shell are the Balmer series. Their emissions are in the visible region and have the shortest wavelengths (400 nm to 700 nm).

The electrons that fall to the (`n=3`) shell are the Paschen series. Their emissions are in the near infrared region and have longer wavelengths (> 700 nm).

The electrons that fall to the (`n=4`) shell are the Brackett series. Their emissions are in the short-wavelength infrared region and have even longer
wavelengths (> 1400 nm).

I have indicated the transitions in the diagram below.

(Adapted from Assignment Point)

In order of decreasing wavelength, the lines are

`color(red)("D") > color(red)("C") > color(red)("B") > color(red)("A")`