KORAKU vs LabOptique
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
KORAKU
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KORAKU is an interactive educational app for exploring optical phenomena through simulation. The fourth in the series following SUUGAKU (Math), BUTURAKU (Physics), and HARAKU (Waves). This time the theme is "Light." From geometrical optics to quantum-scale phenomena, experience ten simulations of how light behaves. [10 Simulations] - Lens (Thin Lens) Observe ray paths and image formation through convex and concave lenses in real time. Adjust focal length, object distance, and object height to experience the thin lens equation (1/f = 1/a + 1/b). - Spherical Mirror Toggle between concave and convex mirrors to visualize image formation. Move the object and change the radius of curvature to see real vs. virtual and upright vs. inverted images. - Prism Dispersion Simulate white light passing through a prism and separating into a rainbow spectrum, based on Snell's law and the Cauchy dispersion formula. - Rainbow Trace light entering a raindrop, refracting, reflecting internally, and exiting. Wavelength-dependent deviation reproduces the primary and secondary rainbows around the antisolar point. - Diffraction Grating Visualize multi-slit interference patterns. Change slit spacing and wavelength to understand the diffraction condition d sin(θ) = mλ. - Optical Fiber Simulate light propagation by total internal reflection. Adjust the launch angle and refractive indices to learn the relationship between critical angle and numerical aperture (NA). - Polarization Change the angles of the polarizer and analyzer to observe transmitted light intensity following Malus's law (I = I₀cos²θ). - Thin Film Interference Reproduce the rainbow colors of soap bubbles and oil films. Adjust film thickness, refractive index, and incident angle to observe interference based on optical path difference. - Color Mixing Compare additive color mixing (RGB light) and subtractive color mixing (CMY pigments). Three channel sliders show the resulting RGB values in real time. - Photoelectric Effect Animate electrons being ejected from a metal by photons. Three sliders for frequency, intensity, and work function let you feel the relationships E = hf, Kₘₐₓ = hf − W, and threshold f₀ = W/h. [Features] - Adjust parameters in real time across all simulations - Physics formulas and values displayed in real time - Dark mode / Light mode support - Japanese / English support - iPhone / iPad support [Pricing & In-App Purchases] - The app itself is completely free - No in-app purchases of any kind - No subscriptions - No paid additional content - A small banner ad (Google AdMob) is shown at the bottom of the screen - Ad personalization may use the iOS App Tracking Transparency permission (optional) [Recommended For] - Students studying optics in physics class - Anyone who wants to intuitively understand the properties of light - Teachers looking for teaching materials - Anyone interested in optics
LabOptique
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Examine various aspects of geometric and wave optics: - Geometric optics: thin lenses, the concept of approximate stigmatism, depth of field, vision of the eye (accommodation, etc.). Possibility of combining multiple lenses, an eye... - Wave optics: from the concept of path difference (for senior year students) to the effects of a glass plate, the concept of coherence length..., in various situations: infinitely narrow or wide Young’s slits or holes, freely movable sources to recreate a Michelson interferometer, a diffraction grating, a Lloyd mirror, using either a monochromatic source or white light.
Screenshots
Verdict
The clearest difference is ads: LabOptique at none against KORAKU's shown. KORAKU's advantage is update cadence (weekly vs every 3 months) and iOS requirement (13.0 vs 15.0). On price, in-app purchases and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Neither carries in-app purchases, so what you see is what you pay.
KORAKU ships an update weekly, LabOptique every 3 months. The most recent releases landed on September 14, 2026 and September 18, 2026 respectively.
| Parameter | KORAKU | LabOptique |
|---|---|---|
| Price | Free | Free |
| Update frequency | Weekly — better | Every 3 months |
| Ads | Yes | No — better |
| In-app purchases | No | No |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Requires iOS | 13.0 — better | 15.0 |
| Further details — not scored | ||
| Size | 24 MB | 7 MB |
| Age rating | 4+ | 4+ |
| Developer | Fuji Bit Inc. | Thomas Roy |
In-app purchases
KORAKU
No in-app purchases
LabOptique
No in-app purchases









