Skip to ContentGo to accessibility page
OpenStax Logo
Physics

Key Terms

PhysicsKey Terms

Key Terms

aberration
a distortion in an image produced by a lens
angle of incidence
the angle, with respect to the normal, at which a ray meets a boundary between media or a reflective surface
angle of reflection
the angle, with respect to the normal, at which a ray leaves a reflective surface
angle of refraction
the angle between the normal and the refracted ray
central axis
a line perpendicular to the center of a lens or mirror extending in both directions
chromatic aberration
an aberration related to color
concave lens
a lens that causes light rays to diverge from the central axis
concave mirror
a mirror with a reflective side that is curved inward
converging lens
a convex lens
convex lens
a lens that causes light rays to converge toward the central axis
convex mirror
a mirror with a reflective side that is curved outward
critical angle
an incident angle that produces an angle of refraction of 90°
dispersion
separation of white light into its component wavelengths
diverging lens
a concave lens
focal length
the distance from the focal point to the mirror
focal point
the point at which rays converge or appear to converge
incident ray
the incoming ray toward a medium boundary or a reflective surface
index of refraction
the speed of light in a vacuum divided by the speed of light in a given material
law of reflection
the law that indicates the angle of reflection equals the angle of incidence
law of refraction
the law that describes the relationship between refractive indices of materials on both sides of a boundary and the change in the path of light crossing the boundary, as given by the equation n1 sin θ 1 θ 1 = n2 sin θ 2 θ 2
ray
light traveling in a straight line
real image
an optical image formed when light rays converge and pass through the image, producing an image that can be projected onto a screen
refracted ray
the light ray after it has been refracted
Snell’s law
the law of refraction expressed mathematically as n 1 sin θ 1 = n 2 sin θ 2 n 1 sin θ 1 = n 2 sin θ 2
total internal reflection
reflection of light traveling through a medium with a large refractive index at a boundary of a medium with a low refractive index under conditions such that refraction cannot occur
virtual image
the point from which light rays appear to diverge without actually doing so
PreviousNext
Order a print copy
Citation/Attribution
Reuse and redistribution of this content in digital or print format:
  • This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's prior written permission.
  • This book uses the Creative Commons Attribution License, which means that you can reuse and modify the material only for noncommercial purposes, must attribute Texas Education Agency (TEA), and must distribute any derivative works under the same license. The original material is available at: https://www.texasgateway.org/book/tea-physics . Changes were made to the original material, including updates to art, structure, and other content updates.
  • Any commercial printing of this textbook, including using a local or custom printer, must be approved by OpenStax, and proper citation provided.
  • OpenStax-copyrighted images, activities, assessments, and similar components of this book are subject to the same licensing – CC-BY-NC-SA. They can be used for noncommercial purposes with attribution. Commercial use requires permission.
  • Permission requests: Anyone who intends to incorporate this content (including text, images, and other components) into large language models, use it in AI offerings, use it commercially (including in print), and/or has questions about another use case is welcome to complete our reuse request form.
Attribution information
  • If you are redistributing all or part of this book in a noncommercial print format, then you must include on every physical page the following attribution:

    Access for free at https://openstax.org/books/physics/pages/1-introduction

  • If you are redistributing all or part of this book in a noncommercial digital format, then for every page that includes OpenStax content, you must license the derivative work under the same CC-BY-NC-SA license as the original, and include on every digital page view the following attribution:

    Access for free at https://openstax.org/books/physics/pages/1-introduction

Citation information

The information below includes the information needed to generate citations in most major styles (APA, MLA, etc.); you must reformat and organize the information as needed to fit the requirements of the style. Use the information below to generate a citation. We recommend using a citation tool such as this one.

© Jul 8, 2026 Texas Education Agency (TEA). The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo, and Rice University name, and Rice University logo trademarks, or wordmarks are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.