Optics and Light Physics Lesson 34 by Owen Borville 1.11.2026
The ray model of light describes a ray as a straight line that originates at some point. The study of optics that deals with the ray aspect of light is called geometric optics.
Light can travel in three ways from a source to a different location (1) directly from the source through empty space, (2) through different media, (3) and after being reflected from a mirror.
The law of reflection states that when a light ray strikes a smooth surface, the angle of reflection equals the angle of incidence (θr = θi). A mirror has a smooth surface and reflects light at specific angles. Light is diffused when it reflects from a rough surface. Mirror images can be photographed and videotaped by instruments.
The law of refraction (Snell's law) relates the indices of refraction for two media at an interface to the change in angle of a light ray passing through that interface. Refraction involves the changing of a light ray's direction when it passes through variations in matter. The speed of light in a vacuum c = 2.99 x 10^8 or approximately 3.00 x 10^8 m/s.
The index of refraction n = c/v, where v is the speed of light in the material, c is the speed of light in a vacuum, and n is the index of refraction.
Snell's law, the law of refraction in equation form is n1sinθ1 = n2sinθ2. The critical angle is the incident angle that produces an angle of refraction of 90 degrees. The critical angle θc = sin-1(n2/n1) for n1>n2.
Total internal reflection is a phenomenon that occurs at the boundary between two media (mediums), such that if the incident angle in the first medium is greater than the critical angle, then all light is reflected back into that medium.
Fiber optics involves the transmission of light down fibers of plastic or glass, applying the principle of total internal reflection. Endoscopes are used to explore the body through various orifices (openings) or minor incisions, based on the transmission of light through optical fibers. Cladding prevents light from being transmitted between fibers in a bundle. Diamonds sparkle due to total internal reflection and with a large index of refraction.
Dispersion is the spreading of white light into its full spectrum of wavelengths. Rainbows are produced by a combination of refraction and reflection and involve the dispersion of sunlight into a continuous distribution of colors. Dispersion produces rainbows but also causes problems in certain optical systems.
Huygens's principle states that every point on a wave front is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wave front is tangent to all of the wavelets. A mirror reflects an incoming wave at an angle equal to the incident angle, verifying the law of reflection. The law of refraction can be explained by applying Huygens's principle to a wave front passing from one medium to another. The bending of a wave around the edges of an opening or an obstacle is called diffraction.
Polarization is the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave. Electromagnetic waves are transverse waves that may be polarized. The direction of polarization is defined to be the direction parallel to the electric field of the EM wave.
Unpolarized light is composed of many rays having random polarization directions. Unpolarized light can be polarized by passing it through the polarizing filter or other polarizing material. The process of polarizing light decreases its intensity by a factor of 2.
The intensity, I, of polarized light after passing it through a polarizing filter is I = I0cos^2θ (Malus's law), where Io is the incident or original intensity and θ is the angle between the direction of polarization and the axis of the filter. Polarization is also produced by reflection.
Brewster's law states that reflected light is completely polarized at the angle of reflection θb, known as Brewster's angle. Brewster's law = tan θb = n2/n1, where n1 is the medium in which the incident and reflected light travel and n2 is the index of refraction of the medium that forms the interface that reflects the light.
Polarization can also be produced by scattering. Several types of optically active substances rotate the direction of polarization of light passing through them.
The ray model of light describes a ray as a straight line that originates at some point. The study of optics that deals with the ray aspect of light is called geometric optics.
Light can travel in three ways from a source to a different location (1) directly from the source through empty space, (2) through different media, (3) and after being reflected from a mirror.
The law of reflection states that when a light ray strikes a smooth surface, the angle of reflection equals the angle of incidence (θr = θi). A mirror has a smooth surface and reflects light at specific angles. Light is diffused when it reflects from a rough surface. Mirror images can be photographed and videotaped by instruments.
The law of refraction (Snell's law) relates the indices of refraction for two media at an interface to the change in angle of a light ray passing through that interface. Refraction involves the changing of a light ray's direction when it passes through variations in matter. The speed of light in a vacuum c = 2.99 x 10^8 or approximately 3.00 x 10^8 m/s.
The index of refraction n = c/v, where v is the speed of light in the material, c is the speed of light in a vacuum, and n is the index of refraction.
Snell's law, the law of refraction in equation form is n1sinθ1 = n2sinθ2. The critical angle is the incident angle that produces an angle of refraction of 90 degrees. The critical angle θc = sin-1(n2/n1) for n1>n2.
Total internal reflection is a phenomenon that occurs at the boundary between two media (mediums), such that if the incident angle in the first medium is greater than the critical angle, then all light is reflected back into that medium.
Fiber optics involves the transmission of light down fibers of plastic or glass, applying the principle of total internal reflection. Endoscopes are used to explore the body through various orifices (openings) or minor incisions, based on the transmission of light through optical fibers. Cladding prevents light from being transmitted between fibers in a bundle. Diamonds sparkle due to total internal reflection and with a large index of refraction.
Dispersion is the spreading of white light into its full spectrum of wavelengths. Rainbows are produced by a combination of refraction and reflection and involve the dispersion of sunlight into a continuous distribution of colors. Dispersion produces rainbows but also causes problems in certain optical systems.
Huygens's principle states that every point on a wave front is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The new wave front is tangent to all of the wavelets. A mirror reflects an incoming wave at an angle equal to the incident angle, verifying the law of reflection. The law of refraction can be explained by applying Huygens's principle to a wave front passing from one medium to another. The bending of a wave around the edges of an opening or an obstacle is called diffraction.
Polarization is the attribute that wave oscillations have a definite direction relative to the direction of propagation of the wave. Electromagnetic waves are transverse waves that may be polarized. The direction of polarization is defined to be the direction parallel to the electric field of the EM wave.
Unpolarized light is composed of many rays having random polarization directions. Unpolarized light can be polarized by passing it through the polarizing filter or other polarizing material. The process of polarizing light decreases its intensity by a factor of 2.
The intensity, I, of polarized light after passing it through a polarizing filter is I = I0cos^2θ (Malus's law), where Io is the incident or original intensity and θ is the angle between the direction of polarization and the axis of the filter. Polarization is also produced by reflection.
Brewster's law states that reflected light is completely polarized at the angle of reflection θb, known as Brewster's angle. Brewster's law = tan θb = n2/n1, where n1 is the medium in which the incident and reflected light travel and n2 is the index of refraction of the medium that forms the interface that reflects the light.
Polarization can also be produced by scattering. Several types of optically active substances rotate the direction of polarization of light passing through them.