CIE A Level Physics复习笔记22.3.3 Calculating Discrete Energies

• The difference between two energy levels is equal to a specific photon energy
• The energy (hf) of the photon is given by:

ΔE = hf = E₂ - E₁

• Where,
  • E₁ = Energy of the higher level (J)
  • E₂ = Energy of the lower level (J)
  • h = Planck’s constant (J s)
  • f = Frequency of photon (Hz)
• Using the wave equation, the wavelength of the emitted, or absorbed, radiation can be related to the energy difference by the equation:

• This equation shows that the larger the difference in energy of two levels ΔE , the shorter the wavelength λ and vice versa

Part (a)

Photon energy and wavelength are inversely proportional, so the largest energy change corresponds to the shortest wavelength (line S) and the smallest energy change corresponds to the longest wavelength (line L)

Part (b)

Step 1:            Write down the equation linking the wavelength and the energy levels

Step 2:            Identify the energy levels giving rise to the shortest wavelength

E₁ = 0.54 eV

E₂ = 3.4 eV

Step 3:            Calculate the wavelength

To convert from eV → J: multiply by 1.6 × 10^-19