Lesson Plan

• Describe the wavelength and frequency limits of visible light.
• Explain how cone photoreceptors define the visible spectrum.
• Apply the relation c = λ f to calculate frequencies for given visible wavelengths.
• Analyse practical implications of the visible range for lighting design and eye safety.
• Evaluate how spectrophotometers use the 400–700 nm band to measure colour.

• Projector or interactive whiteboard
• PowerPoint slides showing the EM spectrum and visible band
• Printed handout of wavelength‑frequency table
• LED light sources of different colours
• Spectrophotometer (or simulation software)
• UV/IR safety goggles

Begin with a quick poll: “What colours can you see in a rainbow and why?” Connect this to prior knowledge of the EM spectrum. State that today’s success criteria are to identify the visible wavelength range, relate it to frequency, and explain its relevance to everyday technology and safety.

1. Do‑now (5 min): Students list EM spectrum regions on sticky notes and place them in order.
2. Mini‑lecture (10 min): Present the 400–700 nm visible band, cone types, and the equation c = λ f with sample calculations.
3. Interactive simulation (10 min): Use an online tool to vary wavelength and observe the corresponding colour and frequency.
4. Group calculation activity (15 min): Teams calculate frequencies for 450 nm, 550 nm, and 650 nm and discuss how colour perception changes.
5. Practical demo (10 min): Show LED colours and a spectrophotometer read‑out; discuss why UV/IR protection is needed.
6. Check for understanding (5 min): Exit ticket – one sentence explaining why only 400–700 nm is visible.

Recap the visible wavelength limits, the link to frequency, and the role of cone cells. Collect exit tickets to gauge retention and assign homework: a short report on how LED lighting design uses the visible spectrum.