Light & Lenses: How Optics Shape What We See
Bend light. Focus images. See the world differently.
Bend light. Focus images. See the world differently.
Light travels at different speeds through different materials. When it crosses a boundary (like air to glass), it changes direction. This bending is called refraction. Drag the angle slider to see how the bend changes.
A convex lens is thicker in the middle. It bends parallel light rays inward to meet at a focal point. Move the object to see how the image changes: it can be larger, smaller, upside down, or right-side up depending on distance.
Real, inverted, smaller image.
Your eye's lens is convex. It focuses light onto your retina to form an upside-down image. Your brain interprets the signal correctly without ever needing to "flip" it, so you never notice.
A concave lens is thinner in the middle. It bends light rays outward, making them diverge. The image is always virtual, upright, and smaller. This is how nearsighted glasses work: they spread light before it enters the eye.
Virtual, upright, smaller image.
Every lens you interact with daily uses the same refraction physics you just explored.
Convex lenses correct farsightedness (can't see close). Concave lenses correct nearsightedness (can't see far). Billions of people depend on this daily.
A camera lens focuses light onto a sensor. Zoom lenses change focal length. Wide-angle lenses have short focal lengths, telephoto lenses have long ones.
Two convex lenses in series. The objective lens creates a magnified image, then the eyepiece magnifies it again. Total magnification = lens 1 * lens 2.
A large convex lens collects light from distant objects and focuses it. The Hubble telescope's mirror (a reflective "lens") is 2.4 meters across.
You've seen how a simple curved piece of glass can bend light, focus images, and power everything from eyeglasses to telescopes. The same physics that corrects your vision also lets us see galaxies billions of light-years away.
When light passes from one material to another (air to glass), it changes speed and bends. This is refraction.
A convex (bulging) lens bends light inward toward a focal point. This is how magnifying glasses, cameras, and your eyes work.
A concave (caved-in) lens spreads light outward. Used to correct nearsightedness and in peepholes.
Shorter focal length = stronger lens = more bending. Camera zoom is just changing the focal length.
Put your new knowledge into practice!