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Light, Reflection, and Lenses: 6 Optics Basics Explained

Tap through each topic in order to see how light, reflection, and lenses actually work.

  1. The Law of Reflection

    When light hits a smooth, mirror-like surface, the angle of incidence always equals the angle of reflection β€” this is exactly why you can see your reflection in a mirror.

  2. Refraction and Snell's Law

    When light passes from one medium into another of different density β€” like air into water β€” its speed changes and its path bends. This is described by Snell's Law: n₁·sinθ₁ = nβ‚‚Β·sinΞΈβ‚‚.

  3. Total Internal Reflection and Fiber Optics

    When light traveling in a denser medium strikes a less-dense medium at an angle greater than the critical angle, it doesn't refract at all β€” it reflects 100%. This principle is the core of fiber-optic communication, which carries light signals over long distances without loss.

  4. Convex Lenses β€” Lenses That Converge Light

    A convex lens, thicker in the middle, bends parallel incoming light rays so they converge at a single point (the focal point). It is used in magnifying glasses and in eyeglasses that correct farsightedness.

  5. Concave Lenses β€” Lenses That Spread Light

    A concave lens, thinner in the middle, spreads incoming light rays apart so they never converge to a focal point. It is used in eyeglasses that correct nearsightedness (myopia).

  6. Dispersion β€” Why a Prism Creates a Rainbow

    Light refracts by a slightly different amount depending on its wavelength, so when white light (a mix of all colors) passes through a prism, it splits into red, orange, yellow, green, blue, indigo, and violet.

The Same Principle Behind Prescription Eyeglasses

Opticians classify corrective lenses as convex or concave based on exactly this refraction principle. Depending on which way a lens bends incoming light, it corrects either farsightedness or nearsightedness.

Curious How Rainbows Actually Form?

This same light-dispersion principle is what creates a rainbow in the sky β€” countless raindrops each acting like a tiny prism, splitting sunlight into its component colors.

Frequently Asked Questions

Is the reason a leg looks shorter underwater also due to refraction?

Yes. Light reflecting off your leg underwater bends (refracts) as it passes from water into air, making your leg appear shorter and shallower than it actually is.

Why do fiber-optic cables rely on total internal reflection?

Fiber-optic cables need to carry light signals over long distances without the signal leaking out or weakening. They're built so that, thanks to the difference in refractive index between the core and the cladding, light reflects completely at the boundary instead of escaping.