Optics & Waves · GCSE Physics Topic 6
Prism Dispersion & Rainbow Spectrum Simulator
Key exam takeaway: White light is composite. In glass, red light has longer wavelength, smallest refractive index and bends least; violet light bends most.
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Parameter Controls
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Live Derivations & Metrics
Red Deviation Angle
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Violet Deviation Angle
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Dispersion Spread Δδ
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Minimum Deviation Angle
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Real-Time Formula Derivation
Governing Formula:
--Substitution:
--Regime: --
Worked Examples & Exam Question Deep Dive
Worked Problem
Problem: Why does red appear on top and violet on bottom after prism dispersion?
Step-by-Step Derivation:
- Violet has shortest wavelength and highest refractive index, experiencing greater deviation than red.
Worked Problem
Problem: What are the 3 primary colors of light vs pigment? What colors do their equal mixtures produce?
Step-by-Step Derivation:
- Primary light: Red, Green, Blue (additive, mixes to white). Primary pigment: Cyan, Magenta, Yellow (subtractive, mixes to black).
Student Inquiry Worksheet & Practice Problems
Q1. Variant 1: What invisible rays lie outside red and violet ends? Give practical applications.
Answer Key: Outside red is infrared (thermal imaging, remote controls). Outside violet is ultraviolet (sterilization, counterfeit detection).
Q2. Variant 2: How did Newton prove that prisms do not dye white light?
Answer Key: 1) Monochromatic ray test: Isolated red light does not split in a second prism; 2) recombination: an inverted second prism merges colors back to white.
Q3. Variant 3: Under a magnifying glass, what 3 subpixel phosphor dots compose a color TV screen?
Answer Key: Red, Green, and Blue (RGB) dots. Modulating their individual intensities synthesizes all visible colors.
Frequently Asked Questions & Misconceptions
Why is the sky blue and sunset red?
Rayleigh scattering. Short blue wavelengths scatter strongly across the sky. At sunset, light traverses thicker atmosphere; only long red wavelengths penetrate.
Why are rainbows only visible looking away from the sun?
Rainbows are formed by raindrops retro-reflecting sunlight at ~42°. The observer must face away from the sun toward the rain curtain.
Do infrared thermometer guns shoot infrared rays at your head?
No! All objects above absolute zero emit thermal infrared radiation. The gun passively absorbs body infrared photons to compute temperature.
What determines the color of transparent vs opaque objects?
Transparent: the color of light transmitted (red glass passes red). Opaque: the color of light reflected (green leaves reflect green). White reflects all, black absorbs all.