25.2 The Law of Reflection
2 min read•june 18, 2024
Light is a fundamental concept in optics. It explains how light bounces off surfaces, creating images we see daily. Understanding reflection helps us grasp how mirrors work and why objects appear the way they do.
The states that the equals the . This principle applies to both smooth and rough surfaces, affecting how light is scattered. It's crucial for understanding image formation in mirrors and other reflective objects.
The Law of Reflection
Reflection from surface types
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- Smooth surfaces
- Reflect light uniformly and predictably
- Incident rays hitting at the same angle will reflect at the same angle ()
- Examples: plane mirrors, polished metal, still water
- Rough surfaces
- Reflect light in various directions due to irregular surface
- Incident rays hitting at the same angle will reflect at different angles ()
- Examples: paper, matte paint, unpolished wood
Wave Optics and Reflection
- are part of the electromagnetic spectrum
- Reflection occurs when light waves bounce off a surface
- The law of reflection applies to both particle and wave models of light
Calculations with reflection law
- Law of reflection states angle of incidence equals angle of reflection
- is angle of incidence, measured between and
- is angle of reflection, measured between and normal
- Normal is imaginary line perpendicular to surface at point of incidence
- To calculate angle of reflection, measure angle of incidence and use law of reflection
- To calculate angle of incidence, measure angle of reflection and use law of reflection
- The incident ray, reflected ray, and normal all lie in the same plane
Formation of mirror images
- formed by reflection of light from mirror's surface
- Image appears behind mirror because brain interprets light as coming from point behind mirror
- Due to way reflected light rays converge and appear to originate from behind mirror
- Distance between object and mirror equals apparent distance between image and mirror
- Explains why image appears same size as object
- Characteristics of mirror images
- Virtual: cannot be projected onto a screen
- Upright: not inverted
- Laterally inverted: left and right sides are swapped
Key Terms to Review (17)
$\theta_i = \theta_r$: The law of reflection states that the angle of incidence ('$\theta_i$') is equal to the angle of reflection ('$\theta_r$'). This means that the angle at which a light ray strikes a surface is the same as the angle at which the light ray reflects off the surface.
Angle of Incidence: The angle of incidence is the angle at which a ray of light or other wave strikes a surface. It is the angle between the incident ray and the normal (perpendicular) to the surface at the point of incidence. This term is crucial in understanding the behavior of light and waves as they interact with different mediums and surfaces.
Angle of Reflection: The angle of reflection is the angle at which a ray of light or other wave is reflected from a surface. It is a fundamental concept in the study of optics and the behavior of light, and is closely related to the law of reflection.
Diffuse Reflection: Diffuse reflection is the scattering of light or other electromagnetic radiation from a surface, in which the reflected rays are randomly distributed rather than reflected at a single angle as in the case of specular reflection. This phenomenon occurs when light encounters a rough or irregular surface.
Incident Ray: The incident ray is the path that a light ray takes as it strikes a surface or interface between two different mediums. It is the initial ray of light that encounters the reflecting surface before it is reflected.
Intensity reflection coefficient: The intensity reflection coefficient is a measure of the fraction of incident acoustic wave intensity that is reflected at the boundary between two different media. It is a dimensionless quantity and ranges from 0 to 1.
Law of Reflection: The law of reflection states that when a ray of light reflects off a surface, the angle of reflection is equal to the angle of incidence. This principle governs the behavior of light when it interacts with reflective surfaces and is a fundamental concept in understanding the formation of images by mirrors.
Light Rays: Light rays are the paths that light travels through space. They are imaginary lines that represent the direction and propagation of light, and are fundamental to understanding the behavior of light in various optical phenomena.
Mirror Images: Mirror images refer to the reflection of an object or image in a reflective surface, such as a mirror. The reflected image appears to be an exact copy of the original, but it is reversed along the axis perpendicular to the reflective surface, creating a symmetrical, flipped representation.
Normal: In physics, the term 'normal' refers to a line or surface that is perpendicular or at right angles to another line or surface. It is a fundamental concept in the study of reflection, refraction, and other wave phenomena.
Plane Mirror: A plane mirror is a flat, smooth reflective surface that produces an image of an object by reflecting light. It is a fundamental optical device used in various applications, including mirrors in everyday life, telescopes, and other optical instruments.
Reflected Ray: A reflected ray is the path taken by light after it bounces off a surface, following the principles of reflection. This ray is crucial in understanding how light interacts with different materials and plays a significant role in forming images in mirrors and other reflective surfaces. The angle at which the light strikes the surface, known as the angle of incidence, directly influences the direction of the reflected ray.
Reflection: Reflection is the change in direction of a wave, such as light or sound, when it encounters a boundary or surface. It is a fundamental concept in physics that describes how waves interact with different media and surfaces, leading to various phenomena observed in the physical world.
Specular Reflection: Specular reflection is a type of reflection where the angle of reflection is equal to the angle of incidence, and the reflected light forms a mirror-like image. This phenomenon is governed by the law of reflection, which states that the angle of reflection is equal to the angle of incidence.
Virtual image: A virtual image is an image formed by rays that appear to converge but do not actually meet. It cannot be projected onto a screen because the light rays only seem to come from the image location.
Virtual Image: A virtual image is an image that appears to exist in a different location than the actual object, but does not physically exist in that location. It is an image that is formed when light rays diverge or appear to diverge from a point, but do not actually intersect at that point.
Wave Optics: Wave optics is a branch of physics that describes the behavior of light as a wave phenomenon. It encompasses the principles of reflection, diffraction, interference, and the wave-like properties of light, which are essential in understanding various optical phenomena and applications.