光楽

KORAKU is an educational simulation app that allows users to interactively experience optical phenomena.

This is the fourth installment in the series, following SUUGAKU (Mathematics), BUTURAKU (Objects), and HARAKU (Waves). This time, the theme is "Light." Through 10 different simulations, you can learn about the behavior of light, from geometrical optics to quantum phenomena, while having fun.

【10 Simulations】

■ Lens (Thin Lens)
Observe the optical path and image formation of convex and concave lenses in real time. By freely changing the focal length, object distance, and object height, you can experience the formula for thin lenses (1/f = 1/a + 1/b).

■ Spherical Mirror
Switch between concave and convex mirrors to visualize the image formation of a spherical mirror. By changing the radius of curvature and object distance, you can observe how real and virtual images, and inverted and upright images, switch.

■ Prism Dispersion
Simulates how white light passes through a prism and separates into a rainbow spectrum. The spectrum is plotted based on Snell's law and Cauchy dispersion.

■ Rainbow
Tracks the path of light entering a raindrop, from refraction and internal reflection to refraction and exit. Reproduces the angles and color order of the primary and secondary rainbows centered on the antisolar point based on the deflection angle for each wavelength.

■ Diffraction Grating
Visualizes multi-slit interference patterns. By changing the slit spacing and wavelength, you can intuitively understand the diffraction condition d sin(θ) = mλ.

■ Optical Fiber
Simulates the propagation of light by total internal reflection. By changing the angle of incidence and refractive index, you can learn the relationship between the critical angle and numerical aperture (NA).

■ Polarization
By changing the angles of the polarizer and analyzer, you can observe the change in light transmission intensity according to Malus's law (I = I₀cos²θ).

■ Thin Film Interference
Reproduces the iridescent colors of soap bubbles and oil films. By changing the film thickness, refractive index, and angle of incidence, you can observe interference colors due to optical path differences.

■ Primary Colors (Color Mixing)
Compare additive color mixing of the three primary colors of light (RGB) and subtractive color mixing of the three primary colors of pigments (CMY) by switching modes. Adjust each component with three sliders and check the RGB value of the composite color in real time.

■ Photoelectric Effect
Animate the phenomenon of electrons being emitted when light is shone on a metal. By changing the frequency, light intensity, and work function, you can experience the relationship between E = hf, Kₘₐₓ = hf − W, and threshold frequency f₀ = W/h in a graph.

【Features】
• Real-time parameter adjustment for all simulations
• Real-time display of physical formulas and values
• Dark mode / Light mode support
• Japanese / English support
• Android smartphone / tablet support

【Pricing and Billing】
• The app itself is completely free
• There are no in-app purchases
• There are no subscriptions
• There are no additional content purchases
• A small banner ad (Google AdMob) is displayed at the bottom of the screen

【Recommended for】
• Students studying optics in physics classes
• Those who want to intuitively understand the properties of light
• Teachers who want to use it as teaching material
• Anyone interested in optics