Glossary
Absorption
The process by which light energy is taken up by matter and converted into other forms of energy, typically heat.
Example:
Wearing a black shirt on a sunny day makes you feel warmer due to the Absorption of most visible light wavelengths.
Amplitude (A)
The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. For light, it relates to the intensity or brightness.
Example:
Turning up the brightness on a flashlight increases the Amplitude of the light waves it emits.
Angular Frequency (ω)
A measure of the rate of change of the phase of a wave, defined as 2π times the frequency.
Example:
The Angular Frequency is useful for describing the rotational motion of a point on a wave as it propagates.
Concave (Diverging) Lenses
Lenses that are thinner in the middle and cause parallel light rays to spread out as if originating from a single focal point.
Example:
Eyeglasses for nearsightedness often use Concave Lenses to correct vision by diverging light before it reaches the eye.
Concave Mirrors
Mirrors with a reflecting surface that curves inward, capable of forming both real and virtual images depending on object placement.
Example:
The large mirrors used in reflecting telescopes are Concave Mirrors designed to gather and focus light from distant stars.
Constructive Interference
Occurs when two waves in phase combine, resulting in a wave with a larger amplitude (e.g., a brighter region for light).
Example:
In a double-slit experiment, the bright fringes are areas of Constructive Interference.
Convex (Converging) Lenses
Lenses that are thicker in the middle and cause parallel light rays to converge to a single focal point.
Example:
Magnifying glasses use a Convex Lens to make objects appear larger.
Convex Mirrors
Mirrors with a reflecting surface that curves outward, always forming virtual, upright, and reduced images.
Example:
The passenger-side mirror on a car is often a Convex Mirror to provide a wider field of view, though objects appear closer than they are.
Destructive Interference
Occurs when two waves out of phase combine, resulting in a wave with a smaller or zero amplitude (e.g., a darker region for light).
Example:
The dark fringes in a double-slit experiment are areas of Destructive Interference.
Diffraction
The bending of waves as they pass around obstacles or through small apertures.
Example:
When light passes through a narrow slit, it spreads out, creating a Diffraction pattern rather than a sharp shadow.
Electromagnetic Radiation (EM Spectrum)
A spectrum of waves consisting of oscillating electric and magnetic fields, ranging from radio waves to gamma rays. Light is a small part of this spectrum.
Example:
Your phone uses Electromagnetic Radiation in the microwave range to send and receive signals.
Focal Length (f)
The distance from the center of a lens or mirror to its focal point, where parallel light rays converge or appear to diverge from.
Example:
A camera lens with a shorter Focal Length will have a wider field of view.
Frequency (f)
The number of complete wave cycles that pass a given point per unit of time.
Example:
A higher Frequency of light waves corresponds to a bluer color, while a lower frequency corresponds to redder light.
Geometric Optics
The study of light as rays, focusing on how it interacts with lenses and mirrors to form images.
Example:
Designing a telescope lens system relies heavily on principles of Geometric Optics to focus distant starlight.
Image Distance (dᵢ)
The distance from the image to the center of the lens or mirror.
Example:
If the Image Distance is positive, a real image is formed; if negative, a virtual image.
Interference
The phenomenon that occurs when two or more waves superpose to form a resultant wave of greater, lower, or the same amplitude.
Example:
The colorful patterns seen in soap bubbles are caused by the Interference of light waves reflecting off their thin films.
Law of Reflection
States that the angle of incidence of a light ray equals its angle of reflection, both measured relative to the normal of the surface.
Example:
Pool players use the Law of Reflection to predict how a cue ball will bounce off the table's cushions.
Light Waves
Oscillations of electric and magnetic fields that propagate through space, carrying energy.
Example:
The vibrant colors we see are all different Light Waves with varying wavelengths.
Mirror Equation
A formula identical to the thin lens equation, relating the focal length of a mirror to the object distance and the image distance.
Example:
When designing a security mirror for a store, the Mirror Equation helps determine the optimal curvature for a wide view.
Object Distance (d₀)
The distance from the object to the center of the lens or mirror.
Example:
When taking a photo, adjusting the camera's focus changes the Object Distance at which the lens is optimized.
Periodic Waves
Waves that repeat in both space and time, characterized by consistent wavelength, frequency, and period.
Example:
The ripples created by a dropped pebble in a pond are a good illustration of Periodic Waves.
Phase Constant (φ)
A term in a wave equation that specifies the initial phase of a wave at a given reference point and time.
Example:
Two waves might have the same frequency but different Phase Constant values, meaning their peaks and troughs don't align perfectly.
Physical Optics
The study of light's wave nature, including phenomena like interference and diffraction.
Example:
Understanding why a CD shimmers with rainbow colors requires knowledge of Physical Optics.
Real Images
Images formed where actual light rays converge, which can be projected onto a screen.
Example:
The image projected onto a movie screen is a Real Image.
Reflection
The bouncing back of light when it strikes a surface and does not pass through it.
Example:
Seeing your face in a mirror is a direct result of Reflection.
Refraction
The bending of light as it passes from one medium to another due to a change in its speed.
Example:
A straw in a glass of water appears bent at the surface due to Refraction.
Refractive Index (n)
A dimensionless number that describes how fast light travels through a medium, relative to its speed in a vacuum.
Example:
Diamonds have a very high Refractive Index, which contributes to their brilliant sparkle.
Snell's Law
A formula used to describe the relationship between the angles of incidence and refraction, and the refractive indices of two media.
Example:
Engineers use Snell's Law to design optical fibers that guide light efficiently over long distances.
Speed of Light (c)
The constant speed at which all electromagnetic waves travel in a vacuum, approximately 3 x 10⁸ m/s.
Example:
It takes about 8 minutes for sunlight to reach Earth, traveling at the Speed of Light.
Thin Lens Equation
A formula relating the focal length of a thin lens to the object distance and the image distance.
Example:
To determine where an image will form when using a camera lens, one would apply the Thin Lens Equation.
Virtual Images
Images formed where light rays appear to diverge from, but do not actually converge; they cannot be projected onto a screen.
Example:
Your reflection in a flat bathroom mirror is a Virtual Image.
Wave Number (k)
A measure of the spatial frequency of a wave, defined as 2π divided by the wavelength.
Example:
In advanced wave equations, the Wave Number helps describe how many wave cycles fit into a given distance.
Wavelength (λ)
The spatial period of a periodic wave, representing the distance between consecutive corresponding points of the same phase.
Example:
Red light has a longer Wavelength than blue light, which is why it bends less when passing through a prism.