Read what this module is aiming for. Then open the instrument and work through it.
Learning intentions
Curricular competencies
Module 05
Act 1 of 3 · Wave
Light & Energy
A wave on the plate. Drag wavelength or frequency — watch what stays fixed and what moves.
As you explore
What do you notice?
Reminder: How is wavelength related to energy?
How is energy related to removing an electron?
What if we replaced the sodium atom with a bromine atom — how would the simulation change?
Familiar source
Energy in
IE
0.00
Why connect waves to photons?
You just treated light as a wave — wavelength and frequency locked together by
c.
That describes how light travels. It does not yet say how much energy light can deliver when it meets an atom.
To knock an electron loose, what matters is the energy in each interaction — not only the continuous wave picture.
Treating light as a stream of energy packets (photons) lets us link the wave quantities you measured
(λ, f)
to that packet energy. That link is how ionization by light becomes measurable — and it is the tool the next modules use.1
1
Moog, R. S., & Farrell, J. J. (2015). Chemistry: A Guided Inquiry (5th ed.). ChemActivity 7 — Light, Waves, Electrons. The workbook develops photon energy from the wave quantities, then uses that energy to probe atoms.
From the wave to the photon
c = λ · f
Light travels at speed c: wavelength times frequency.
c speed of light m/s
λ wavelength m (or nm)
f frequency s⁻¹ (Hz)
f = c / λ
Same wave equation, solved for frequency — shorter wavelength means higher frequency.
f frequency s⁻¹ (Hz)
c speed of light m/s
λ wavelength m (or nm)
↓ plug into E
E = h ·
f(c / λ)
Photon energy equals Planck’s constant times frequency — each packet’s energy tracks how rapidly the wave oscillates. Substituting f = c/λ plugs the wave picture into energy.
E energy per photon J (or MJ/mol)
h Planck’s constant J·s
f frequency s⁻¹ (Hz)
E = hc / λ
Photon energy written in terms of wavelength — shorter λ means more energy per photon.
E energy per photon J (or MJ/mol)
h Planck’s constant J·s
c speed of light m/s
λ wavelength m (or nm)
h is Planck’s constant — a fixed conversion factor
(6.626 × 10⁻³⁴ J·s) that turns frequency into energy per photon.22
PBS NOVA.
Planck’s Constant.
Shorter wavelength → higher frequency → more energy per photon
989 nm
3.03 × 10¹⁴ Hz
E=h·f=h cλ
—
λ989 nm
f3.03 × 10¹⁴ s⁻¹
c3.00 × 10⁸ m/s
BandVisible
E—
AtomNa · IE₁ 0.50 MJ/mol
c=λ·f
What type of relationship do the variables have with one another? Why?
h = 6.626 × 10⁻³⁴ J·s
Halve the wavelength. What happens to how many cycles pass X each second?
What this was for
The intentions behind this module, and the competencies you just practised. Read each competency statement and decide honestly how well it fits you right now.