# AP Chemistry : Spectroscopy and Electromagnetic Spectrum

## Example Questions

### Example Question #1 : Photoelectron Spectroscopy

What is the energy of a photon that has a wavelength of 540 nm? None of the above    Explanation: ; ; ### Example Question #1 : Spectroscopy And Electromagnetic Spectrum

What transition would emit the longest wavelength of light?

Not enough information given

n = 4 to n = 1

n = 4 to n = 3

n = 3 to n = 1

n = 2 to n = 1

n = 4 to n = 3

Explanation:

Wavelength is inversely proportional to energy.  Since the transition from n=4 to n=3 is the lowest energy transition, it would have the longest wavelength.

### Example Question #3 : Photoelectron Spectroscopy

What photon wavelength can promote a transition from the n = 1 (ground state) to the n = 3 (excited state)?

204 nm

102 nm

408 nm

1 m

306 nm

102 nm

Explanation:   ### Example Question #4 : Photoelectron Spectroscopy

A 3.0 eV light is shined on Gold ( Փ = 5.1 eV), silver (Փ =4.26 eV), Cesium (Փ = 2.1 eV), and Platinum (Փ = 6.35).  If Փ is the work function of the metal, what metal would have electrons ejected?

Ag

Pt

Au, Ag, and Pt

Cs

Au

Cs

Explanation:

The work function is the energy required to remove an electron from a metal.  Only Cs metal has a work function less than the energy of the light.

### Example Question #5 : Photoelectron Spectroscopy

A student has a Blue #1 dye with a molar absorptivity of 1.30 x 105 M-1 cm-1 at 631 nm.  If the student runs this sample through a spectrophotometer and finds it has an absorption of 0.500 what is the dye’s molarity?  Assume a path length of 1.0 cm.         