Lesson Plan

• Recall the relations E = hf, E = hc/λ and p = h/λ and state the required constants.
• Calculate photon energy and momentum for given wavelengths or frequencies.
• Convert photon energy between joules and electron‑volts and interpret the values.
• Explain how photon momentum produces radiation pressure and apply the concept to simple force problems.

• Projector and screen
• Scientific constants handout (h, c, e)
• Worksheets with photon‑energy and momentum problems
• Calculators
• Laser pointer or low‑power laser
• Light‑mill or solar‑sail model
• Spectrometer (optional) or colour filter set

Begin with the striking image of sunlight pushing a tiny sail—demonstrating that light can exert a force. Review that students already know the wave‑speed relation c = λf and basic unit conversion. State that by the end of the lesson they will be able to compute photon energy and momentum and explain radiation pressure.

1. Do‑now (5′): quick quiz on c = λf and unit conversions.
2. Mini‑lecture (10′): derive E = hf, E = hc/λ and p = h/λ; display constants.
3. Guided practice (12′): solve the green‑photon energy and X‑ray momentum examples in pairs.
4. Interactive activity (10′): calculate and plot E versus λ for the visible spectrum.
5. Demonstration (8′): use a light‑mill model to show radiation pressure; discuss the physics.
6. Independent worksheet (10′): problems on photon momentum and radiation‑pressure forces.
7. Check for understanding (5′): exit‑ticket question – “What force does a 2 W laser exert on a perfectly absorbing surface?”

Summarise the key formulas E = hf, E = hc/λ, p = h/λ and the link to radiation pressure. Collect the exit tickets to gauge understanding and assign homework: complete the worksheet on photon energies across the electromagnetic spectrum and bring a one‑page summary of the formulas for the next lesson.