The Nature of Light and Related Concepts (Lecture Notes)

Vocabulary flashcards covering key terms about the nature of light, the electromagnetic spectrum, and concepts related to reflection and materials.

Light

Electromagnetic waves produced by vibrating electric charges with frequencies in the visible range; travels nearly a million times faster than sound in air; transverse waves.

Electromagnetic spectrum

Range of electromagnetic waves from radio to gamma rays, arranged by increasing frequency (or decreasing wavelength).

Frequency

Number of oscillations per second of a wave; for light, the frequency of vibrating electrons equals the light frequency.

Wavelength

Distance between successive crests of a wave; shorter wavelengths correspond to higher frequencies.

Visible light

Portion of the electromagnetic spectrum detectable by the human eye; includes colors from red to violet.

Red

Color with the lowest frequency in the visible spectrum.

Violet

Color with the highest frequency in the visible spectrum.

Infrared

Electromagnetic waves longer than visible light, just below the red end of the spectrum.

Ultraviolet

Higher-frequency light above visible spectrum; can cause sunburns.

X-rays

High-energy electromagnetic waves used in medical imaging and other applications.

Gamma rays

Highest-energy electromagnetic waves in the spectrum.

Reflection

Return of a wave into the original medium after striking a surface; angle of incidence equals angle of reflection.

Law of reflection

Angle of incidence equals angle of reflection.

Plane mirror

Flat mirror; the only axis reversed in the image is the front-back axis.

Virtual image

Image formed behind a mirror where reflected rays appear to converge; as far behind the mirror as the object is in front.

Convex mirror

Mirror that curves outward; virtual image is smaller and closer to the mirror than the object.

Concave mirror

Mirror that curves inward; virtual image is larger and farther away than the object.

Diffuse reflection

Reflection from a rough surface, causing light to scatter in many directions.

Transparent materials

Materials through which light passes in straight lines (e.g., glass, water).

Opaque materials

Materials that do not transmit light; colored glass is opaque to much of white light.

Refraction

Bending of light as it passes from one medium to another due to a change in speed.

Absorption

Process by which light energy is taken up by atoms, potentially converting to heat.

Reemission

Emission of light by atoms after absorbing energy.

Photon

Quantum of light; the energy carrier of light.

Speed of light in vacuum (c)

Speed of light in vacuum, approximately 3 x 10^8 meters per second.

Index of refraction

Ratio of the speed of light in vacuum to its speed in a given medium.

Speed of light in water

Approximately 0.75 c.

Speed of light in glass

Approximately 0.67 c.

Speed of light in diamond

Approximately 0.41 c.

Electromagnetic induction

Process by which changing electric and magnetic fields regenerate each other; underpinning propagation of electromagnetic waves.