What expression gives the amount of light energy (in J per photon) that is converted to other forms between the fluorescence excitation and emission events?

• A. (6.62 × 10-34) × (3.0 × 10^8)
• B. (6.62 × 10-34) × (3.0 × 10^8) × (360 × 10-9)
• C. (6.62 × 10-34) × (3.0 × 10^8) × [1 / (360 × 10-9) - 1 / (440 × 10-9)]
• D. (6.62 × 10-34) × (3.0 × 10^8) / (440 × 10-9)

Answer: (C)

The expression that represents the amount of light energy converted from fluorescence excitation to emission is based on the energy of the photons associated with their respective wavelengths.

When a photon of a specific wavelength is absorbed, it excites an electron to a higher energy state. Upon returning to its ground state, the electron emits a photon, typically at a longer wavelength due to some energy loss during non-radiative transitions (like vibrational relaxation or heat conversion).

To analyze the expression, the Planck constant (6.62 × 10^-34 J·s) is used in conjunction with the speed of light (3.0 × 10^8 m/s) to calculate the energy of a photon. The energy of a photon can be calculated using the formula (E = \frac{hc}{\lambda}), where (h) is the Planck constant and (c) is the speed of light.

The excitation wavelength mentioned (360 nm) and the emission wavelength (440 nm) provide the starting and final states. The energy absorbed at 360 nm is higher (since shorter wavelengths correspond to higher energy) than the energy emitted at 440 nm.

The correct expression, therefore, involves calculating the energy for both wavelengths