Lightelectromagnetic radiation that can be detected by the human eye. Within that broad spectrum the wavelengths visible to humans occupy a very narrow band, from about nanometres nm; billionths of a metre for red light down to about nm for violet light. The spectral regions adjacent to the visible band are often referred to as light also, infrared at the one end and ultraviolet at the other.
The speed of light in a vacuum is a fundamental physical constantthe currently accepted value of which is exactlymetres per second, or aboutmiles per second. The physicist is interested in the physical properties of light, the artist in an aesthetic appreciation of the visual world.
Through the sense of sight, light is a primary tool for perceiving the world and communicating within it.
Properties of Light and Reflection - PowerPoint PPT Presentation
Light from the Sun warms the Earthdrives global weather patterns, and initiates the life-sustaining process of photosynthesis. Indeed, light provides a window on the universe, from cosmological to atomic scales. Almost all of the information about the rest of the universe reaches Earth in the form of electromagnetic radiation. By interpreting that radiation, astronomers can glimpse the earliest epochs of the universe, measure the general expansion of the universe, and determine the chemical composition of stars and the interstellar medium.
Just as the invention of the telescope dramatically broadened exploration of the universe, so too the invention of the microscope opened the intricate world of the cell. The analysis of the frequencies of light emitted and absorbed by atoms was a principal impetus for the development of quantum mechanics. Atomic and molecular spectroscopies continue to be primary tools for probing the structure of matter, providing ultrasensitive tests of atomic and molecular models and contributing to studies of fundamental photochemical reactions.
Light transmits spatial and temporal information. This property forms the basis of the fields of optics and optical communications and a myriad of related technologies, both mature and emerging. Technological applications based on the manipulations of light include lasersholographyand fibre-optic telecommunications systems.
In most everyday circumstances, the properties of light can be derived from the theory of classical electromagnetismin which light is described as coupled electric and magnetic fields propagating through space as a traveling wave. However, this wave theory, developed in the midth century, is not sufficient to explain the properties of light at very low intensities. At that level a quantum theory is needed to explain the characteristics of light and to explain the interactions of light with atoms and molecules.
In its simplest form, quantum theory describes light as consisting of discrete packets of energycalled photons. However, neither a classical wave model nor a classical particle model correctly describes light; light has a dual nature that is revealed only in quantum mechanics. This surprising wave-particle duality is shared by all of the primary constituents of nature e. Since the midth century, a more comprehensive theory of light, known as quantum electrodynamics QEDhas been regarded by physicists as complete.
QED combines the ideas of classical electromagnetism, quantum mechanics, and the special theory of relativity. This article focuses on the physical characteristics of light and the theoretical models that describe the nature of light.There are 22 videos in this category and 49 videos in 7 subcategories. Follow Us. X Login. Remember Me. Forgot Password? X General Topics. When you narrow the search, only videos with checked age data will appear. Embed Video:. Simply give the URL and we will get the embed code automatically, if we support embedding from the site.
Language Arts Mathematics Science Astronomy Chemistry Earth Science Environmental Science Life Sciences Physics AP Physics Introduction to Physics Mechanics States of Matter Waves and Light Simple Harmonic Motion Time Required: 2 hours 30 minutes three minute periods; can be over three days.
Most curricular materials in TeachEngineering are hierarchically organized; i. Some activities or lessons, however, were developed to stand alone, and hence, they might not conform to this strict hierarchy. Related Curriculum shows how the document you are currently viewing fits into this hierarchy of curricular materials. Because of light, we can see color and reflections. A portable glucose meter is one example of medical devices that use color changes to detect body chemicals.
All rights reserved. A deep understanding and exploration of the properties of light has enabled engineers and scientists to illuminate our world with everything from computer monitors, TV screens, and lasers to fiber optic cables and medical devices.
For example, fiber optic cables give us the ability to communicate and transmit data over long distances at high rates by guiding light through refraction. Since first demonstrated in the s, engineers and scientists have adapted fiber optics to many applications, including communication and medical imaging. Portable glucose monitors are one example of medical devices that use color change as a way to detect body chemicals. Before designing a solution to a challenge, engineers conduct research and gather information as a key step in the engineering design process.
Through this legacy cycle lesson, students continue to gather the knowledge necessary to devise solutions to the engineering challenge outlined in lesson 1 of this unit. Each TeachEngineering lesson or activity is correlated to one or more K science, technology, engineering or math STEM educational standards. In the ASN, standards are hierarchically structured: first by source; e.
Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials. Grades 6 - 8. Do you agree with this alignment? Thanks for your feedback! Alignment agreement: Thanks for your feedback!
View aligned curriculum. Students learn about the science and math that explain light behavior, which engineers have exploited to create sunglasses.Light is intimately involved with our daily lives. Many unique properties of light are extremely fascinating.
Here, we will take one step closer to the wonders of light through its well-known basic properties. Light has the properties of a wave and a particle. It is the distance that light travels in one oscillation, and is often expressed using a unit called "nanometer". One nanometer is equal to one billionth of a meter. Our eyes can only see light that is of a wavelength between approximately to nanometers.
This range is called the visible light. The light of other wavelengths includes X-rays, ultraviolet rays, and infrared rays.
Though we cannot see them directly, these are also members of the light family. On the other hand, light also has the property of a particle.
The intensity of the light varies depending on the number of particles. Bright light has many particles while dark light has fewer particles. We can check out the particle property of light by comparing light with sound using a device called oscilloscope.
Sound is known to have the characteristics of a wave. When the intensity or magnitude of sound gradually weakens, the signal of sound becomes smaller and eventually disappears. However, when light gradually weakens, the overall quantity of its signal becomes less yet the few remaining pulses extremely short signals can be detected and the size of these individual signals does not decrease.
Light travels at a speed of aboutkilometers per second. Surprisingly, light can travel around the earth 7. This property of light is utilized in many technical applications such as optical communications which transfer huge data in a very short time.
However, even light, which is faster than anything known to man, can move only 0. In recent years, research of such optical phenomenon that occur in these unbelievably short period of time, is becoming essential in new research fields of physics, chemistry, biology, and others. When in a vacuum such as outer space where no matter is present, light travels straightforward.
However, light behaves in a variety of ways when it comes in contact with water, air, and other matters — it is "absorbed", "transmitted through", "reflected", and "scattered". When light strikes matter, a part of that light is absorbed into the matter a and is transformed into heat energy. The sunlight striking a mountain bounces back in many directions.Stephen A. In order to understand the optical properties of crystals we must first understand something about light and how it interacts with matter.
Light is electromagnetic radiation that has properties of waves. The electromagnetic spectrum can be divided into several bands based on the wavelength. As we have discussed before, visible light represents a narrow group of wavelengths between about nm and nm. Our eyes interpret these wavelengths as different colors. If only a single wavelength or limited range of wavelengths are present and enter our eyes, they are interpreted as a certain color.
If a single wavelength is present we say that we have monochromatic light. If all wavelengths of visible light are present, our eyes interpret this as white light.
If no wavelengths in the visible range are present, we interpret this as dark. Interaction of Light with Matter. The velocity of light, C, in a vacuum is 2. Note that from the equation given above. Note that the value of refractive index will always be greater than 1. Thus, higher density materials will have higher refractive indices. The refractive index of any material depends on the wavelength of light because different wavelengths are interfered with to different extents by the atoms that make up the material.
In general refractive index varies linearly with wavelength. Materials can be divided into 2 classes based on how the velocity of light of a particular wavelength varies in the material.
Air, since it is a gas, is isotropic. The refractive index of air is usually taken as 1.
The basic nature of light
When light strikes an interface between two substances with different refractive indices, two things occur. An incident ray of light striking the interface at an angle, i, measured between a line perpendicular to the interface and the propagation direction of the incident ray, will be reflected off the interface at the same angle, i.
In other words the angle of reflection is equal to the angle of incidence. If the second substance is transparent to light, then a ray of light will enter the substance with different refractive index, and will be refracted, or bent, at an angle r, the angle of refraction.
The angle of refraction is dependent on the angle of incidence and the refractive index of the materials on either side of the interface according to Snell's Law :. Note that if the angle of incidence is 0 o i. There is also an angle, i ccalled the critical angle for total internal reflection where the refracted ray travels along the interface between the two substances.
The fact that refractive indices differ for each wavelength of light produces an effect called dispersion. This can be seen by shining a beam of white light into a triangular prism made of glass. White light entering such a prism will be refracted in the prism by different angles depending on the wavelength of the light. The refractive index for longer wavelengths red are lower than those for shorter wavelengths violet.
This results in the a greater angle of refraction for the longer wavelengths than for the shorter wavelengths. Shown here are the paths taken for a wavelength of nm, angle r and for a wavelength of nm, angle r When the light exits from the other side of the prism, we see the different wavelengths dispersed to show the different colors of the spectrum.
Absorption of Light When light enters a transparent material some of its energy is dissipated as heat energy, and it thus looses some of its intensity.Light is the everyday term we use for electromagnetic radiation within a certain portion of the electromagnetic spectrum, and usually refers to that light which we can see.
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View by Category Toggle navigation. Products Sold on our sister site CrystalGraphics. Title: Properties of Light and Reflection. Tags: light properties reflection. Latest Highest Rated. Title: Properties of Light and Reflection 1 Properties of Light and Reflection 2 Reflection Is the change in direction of a wave when it reaches a surface and bounces off that surface. Medium is the substance through which light travels.
You can use a technique called ray tracing to make ray diagrams. A ray is a straight line with an arrowhead that shows the direction in which light waves are traveling. According to the principle, light follows the path that will take the least time. When light reflects from a surface and stays in the same medium, its speed is constant. The angle of incidence is measured between the incident ray and a perpendicular line drawn from the point of contact of the incident ray at the surface.
Perpendicular line is called the normal. The reflected ray begins at the point of contact. The angle of reflection is measured between the reflected and the normal. The reflected ray always lies on the plane that is defined by the incident ray and the normal.
These laws of reflection apply to light and all other forms of waves sound waves.