Skip to content
Open Model LabInteractive concept
HomeConcept libraryPhysicsOpticsWave Optics
PhysicsOpticsIntermediateStarter track

Concept module

Dispersion / Refractive Index and Color

Use one compact thin-prism bench to see how refractive index can depend on wavelength, why different colors bend by different amounts, and how a bounded prism model separates colors without widening into a full spectroscopy subsystem.

Interactive lab

Loading the live simulation bench.

Progress

Not startedMastery: NewLocal-first

Start exploring and Open Model Lab will keep this concept's progress on this browser first. Challenge mode has 2 compact tasks ready. No finished quick test, solved challenge, or completion mark is saved yet.

Let the live model runChange one real controlOpen What to notice

Try this setup

Jump to a named bench state or copy the one you are looking at now. Shared links reopen the same controls, graph, overlays, and compare context.

Saved setups

Premium keeps named exact-state study setups in your account while stable concept links stay public below.

Checking saved setup access.

This concept can keep using stable links while the saved-setups capability resolves for this browser.

Copy current setup

Stable concept and section links stay public below while exact-state setup sharing stays behind premium.

Stable links

Starter track

Step 4 of 50 / 5 complete

Wave Optics

Earlier steps still set up Dispersion / Refractive Index and Color.

1. Polarization2. Diffraction3. Double-Slit Interference4. Dispersion / Refractive Index and Color+1 more steps

Previous step: Double-Slit Interference.

Start from track beginning

Why it behaves this way

Explanation

This concept keeps dispersion tightly attached to the refraction story you already used on one boundary. The only new idea is that the refractive index does not have to stay the same for every wavelength, so different colors can obey slightly different bending rules in the same material.

One compact thin-prism bench now keeps wavelength, material response, prism angle, outgoing color fan, graph previews, worked examples, prediction mode, and challenge checks on the same bounded model. The goal is to explain prism color separation honestly without widening into a full spectroscopy platform.

Key ideas

01Dispersion means the refractive index depends on wavelength, so shorter visible wavelengths can use a slightly larger n than longer ones in the same material.
02If violet uses the larger refractive index, it bends more strongly than red at the same prism.
03A prism does not create colors from nothing. It separates wavelengths that were already present by bending them by different amounts.
04This page uses a bounded thin-prism model: the graph values and readout card keep the real deviation angles, while the stage lightly magnifies the outgoing fan so the color order stays readable.

Frozen walkthrough

Step through the frozen example

Frozen walkthrough
Read the current prism state directly from the live controls. The same wavelength-dependent index model drives the stage, the outgoing fan, and the response graphs.

Premium unlocks saved study tools, exact-state sharing, and the richer review surfaces that support this guided flow.

View plans
Frozen valuesUsing frozen parameters

For the current wavelength and material, what refractive index does the selected color use?

Selected wavelength

550 nm

Reference index

1.52

Dispersion strength

0.02

1. Start from the bounded dispersion model

Use with wavelengths in nanometers.

2. Evaluate the wavelength term

For , the bracket becomes .

3. Build the current index

.

Current refractive index

At 550 nm, the current green ray uses n(lambda) = 1.52, so the thin-prism bend is larger than red but smaller than violet in the same material.

Prism-spread checkpoint

You keep the same prism angle and the same green reference index, but you raise the dispersion strength. Before touching the controls, which color should peel away the most from the others?

Make a prediction before you reveal the next step.

Answer from the wavelength-dependent index, not from a brightness cue.

Check your reasoning against the live bench.

Violet should separate the most because it uses the largest refractive index in this visible range.
Raising the dispersion strength makes the difference between short- and long-wavelength refractive indices larger. That gives violet the largest bend and widens the outgoing fan most strongly on the short-wavelength side.

Common misconception

A prism paints color onto white light because the glass somehow adds red on one side and violet on the other.

The prism is not adding new visible colors. It is separating wavelengths that were already present in the beam because each wavelength can use a different refractive index in the material.

That is why a no-dispersion model can still bend the beam overall while failing to spread red and violet apart.

Quick test

Variable effect

Question 1 of 4

Answer from the live wavelength-dependent refraction story, not from a vague picture of a rainbow beam.

In a dispersive prism, which visible color bends more at the same prism angle?

Use the live bench to test the result before moving on.

Accessibility

The simulation shows one triangular thin-prism sketch with a white incoming beam, a highlighted selected-color ray, and optional red, green, and violet comparison rays leaving the same prism. A readout card summarizes the current wavelength, reference index, dispersion strength, selected refractive index, selected deviation, speed fraction, red-violet spread, and prism angle.

Optional overlays can show the outgoing color fan, the current ordering of red, green, and violet refractive indices, and the bounded thin-prism approximation used to connect refractive index to total deviation. The stage uses a small display magnification so the color order stays readable while the card and graphs keep the real angle values.

Graph summary

The first graph plots refractive index against visible wavelength for the current material model. The second plots thin-prism deviation against visible wavelength for the same material and prism angle, so hovering either graph previews another wavelength on the same static prism instead of stepping time forward.