Optics

Understanding light, vision, and optical phenomena

Subcategories

Geometric Optics

Understanding reflection, refraction, and how light travels in straight lines

Optical Applications

Understanding how optical principles are applied in technology and instruments

Properties of Light

Understanding the nature of light, color, and the visible spectrum

Wave Optics

Understanding wave properties of light, interference, and diffraction

Topics

Lenses work by refracting (bending) light as it passes through. Convex lenses converge light rays to a focus point, while concave lenses diverge them. This bending occurs because light slows down when entering the lens material.

How does a camera work?

A camera works by using a lens to focus light onto a light-sensitive sensor or film. The lens creates an image, and the sensor/film captures it. A shutter controls how long light enters, and an aperture controls how much light enters.

Why do mirrors reflect?

Mirrors reflect because they have smooth, polished surfaces that bounce light back. When light hits a mirror, it reflects at the same angle it arrived (angle of incidence equals angle of reflection), creating a clear reflection.

Why do we see rainbows?

We see rainbows when sunlight is refracted (bent) and reflected inside water droplets. Different colors bend at different angles due to their wavelengths, separating white light into the spectrum of colors we see as a rainbow.

Why is the sky blue?

The sky is blue because of Rayleigh scattering—sunlight is scattered by tiny particles in the atmosphere, and blue light scatters more than other colors because it has shorter wavelength. This scattered blue light reaches our eyes from all directions, making the sky appear blue.

How do we see color?

We see color through specialized cells in our eyes called cones that detect different wavelengths of light. There are three types of cones sensitive to red, green, and blue wavelengths. Our brain combines signals from these cones to create the perception of all colors.

What is color?

Color is how our eyes and brain perceive different wavelengths of light. Visible light wavelengths range from about 400 nm (violet) to 700 nm (red), with different wavelengths appearing as different colors. Color depends on both the light source and how objects reflect or transmit light.

What is the speed of light?

The speed of light in vacuum is approximately 299,792,458 meters per second (about 186,282 miles per second), often denoted as 'c'. It's the fastest speed possible in the universe and is constant for all observers, regardless of their motion.

What is the visible spectrum?

The visible spectrum is the range of electromagnetic wavelengths that human eyes can detect, approximately 400-700 nanometers. It includes all the colors we can see, from violet (shortest wavelength) through blue, green, yellow, orange, to red (longest wavelength).

Why is light both a wave and a particle?

Light exhibits wave-particle duality—it behaves as both waves and particles depending on how we observe it. Wave behavior appears in interference and diffraction, while particle behavior (photons) appears in interactions with matter. This duality is fundamental to quantum mechanics.

How do holograms work?

Holograms work by recording interference patterns between light from an object and a reference beam. When illuminated, these patterns diffract light to recreate the original light field, creating a 3D image that appears to have depth and can be viewed from different angles.

How do lasers work?

Lasers work by stimulating atoms to emit light in phase, creating coherent light where all waves are synchronized. A laser uses an active medium (like a crystal or gas), energy source to excite atoms, and mirrors to amplify and direct the light into a focused beam.

What is diffraction?

Diffraction is the bending and spreading of waves around obstacles or through openings. When waves encounter an obstacle or opening comparable in size to their wavelength, they bend around it and spread out, creating diffraction patterns.

What is interference?

Interference occurs when two or more waves overlap and combine. Constructive interference happens when waves align (peaks with peaks), creating larger waves, while destructive interference happens when waves cancel (peaks with troughs), creating smaller or zero waves.

What is polarization?

Polarization is the orientation of light's electric field oscillations. Unpolarized light oscillates in all directions, while polarized light oscillates in a specific direction. Polarizers filter light to allow only specific orientations to pass.