Chapter 26: Light and Electromagnetic Waves

Flashcards covering the properties of light, the electromagnetic spectrum, wave-particle duality, and the physics of optics based on lecture notes.

Light

A form of energy that travels as electromagnetic waves and allows us to see the world.

Electromagnetic Wave

A wave produced by a vibrating electrically charged particle that creates electric and magnetic waves moving at a particular speed.

Wave-particle Duality

The concept that light behaves both like a wave (spreading out and forming patterns) and like a particle (tiny packets of energy).

Photons

Small, discrete, individual, mass-less little bundles or packets of energy.

Speed of Light

The speed at which light moves, approximately $300,000,000\,m/s$.

Transverse Wave

The specific type of self-propagating energy wave that characterizes light behavior.

Gamma Rays

The part of the electromagnetic spectrum with the shortest wavelength and highest energy; they are ionizing and blocked by concrete.

X-Ray

High energy waves with slightly longer wavelengths than gamma rays; they are used to create images and are blocked by lead.

Ultra-Violet (UV)

Electromagnetic waves that include UVA (aging), UVB (sunburn), and UVC (killing bacteria); they are blocked by clothing, sunscreen, and glass.

Visible Light

The range of frequencies our eyes can detect, ranging from Blue (highest frequency) to Red (lowest frequency).

Infrared (IR)

Electromagnetic waves associated with heat, used in TV remotes, night vision goggles, and thermal imaging; they are blocked by aluminum.

Microwaves

Non-ionizing waves used for satellite communication, cellphones, and cooking; they are blocked by copper or foil.

Radio Waves

The part of the electromagnetic spectrum with the longest wavelengths and lowest energy, used for radio communication.

Diffraction

The ability of light waves to spread three-dimensionally when they hit a slit or barrier.

Refraction

The bending of light waves as they move from one medium and hit the boundary of another medium.

Reflection

The process of light waves bouncing back when they hit another medium.

Inverse Square Relationship

The mathematical property of waves where illumination ($I$) decreases as the square of the distance increases ($I \propto \frac{1}{d^2}$).

Polarization

The process of filtering light so that it vibrates in only one direction, such as vertical lenses blocking horizontal glare.

Photoelectric Effect

A phenomenon where light shining on a metal surface causes electrons to be released; this serves as evidence for light as a particle.

Opaque Materials

Materials that absorb light without remitting it, such as books, desks, and metals.

Transparent Materials

Materials through which light can pass, occurring when the frequency of the EM wave does not equal the natural frequency of the electrons.

Refractive Index ($n$)

A value ($n = \frac{c}{v}$) that indicates how much light slows down in a material compared to its speed in a vacuum.

Umbra

The darkest part of a shadow where no light reaches.

Penumbra

The lighter, fuzzy edge of a shadow where some light still gets through.

Solar Eclipse

An event where the Moon passes between the Sun and Earth, blocking sunlight and casting a shadow on Earth.

Lunar Eclipse

An event where Earth blocks sunlight from reaching the Moon, often causing the Moon to appear dark or red.

White Light

A combination of all frequencies and wavelengths of the visible spectrum.

Rods

Cells in the eye that show only the presence or absence of light (black or white).

Cones

Cells in the eye responsible for color vision; humans have red, blue, and green types.