File Name: refraction and total internal reflection ppt to .zip
Learning Objectives. Book Reference : Pages Optics: Total Internal Reflection. To understand the concept of T otal I nternal R eflection T. To be able to apply TIR to applications such as fibre optics and gem stones.
Whenever you look into a mirror or squint at sunlight glinting off a lake, you are seeing a reflection. When you look at the text in a book, you are actually seeing the light that is reflected from it. Large telescopes use reflections to form images of stars and other astronomical objects. In fact, the only way we can see an object that does not itself emit light is if that object reflects light.
The law of reflection is illustrated in, which also shows how the angles are measured relative to the perpendicular to the surface at the point where the light ray strikes. The law of reflection is very simple: The angle of reflection equals the angle of incidence.
When we see our reflection in a mirror, it appears that our image is actually behind the mirror — we see the light coming from a direction determined by the law of reflection. The angles are such that our image appears exactly the same distance behind the mirror as we stand away from the mirror.
Mirror Reflection : An image in a mirror appears as though it is behind the mirror. The two rays shown are those that strike the mirror at just the correct angles to be reflected into the eyes of the viewer. The angles are measured relative to the perpendicular to the surface at the point where the ray strikes the surface.
We expect to see reflections off a smooth surface. Diffused light is what allows us to see a sheet of paper from any angle. Many objects, such as people, clothing, leaves, and walls, have rough surfaces and can be seen from all sides. A mirror, on the other hand, has a smooth surface compared with the wavelength of light and reflects light at specific angles.
When the moon reflects off the surface of a lake, a combination of these effects takes place. The amount that a light ray changes its direction depends both on the incident angle and the amount that the speed changes. It is easy to notice some odd things when looking into a fish tank. For example, you may see the same fish appearing to be in two different places. This is because light coming from the fish to us changes direction when it leaves the tank, and in this case, it can travel two different paths to get to our eyes.
Refraction is responsible for a tremendous range of optical phenomena, from the action of lenses to voice transmission through optical fibers. Law of Refraction : Looking at the fish tank as shown, we can see the same fish in two different locations, because light changes directions when it passes from water to air.
In this case, the light can reach the observer by two different paths, and so the fish seems to be in two different places. This bending of light is called refraction and is responsible for many optical phenomena. The speed of light varies in a precise manner with the material it traverses. It makes connections between space and time and alters our expectations that all observers measure the same time for the same event, for example.
The speed of light is so important that its value in a vacuum is one of the most fundamental constants in nature as well as being one of the four fundamental SI units. Why does light change direction when passing from one material medium to another? It is because light changes speed when going from one material to another. A ray of light changes direction when it passes from one medium to another. As before, the angles are measured relative to a perpendicular to the surface at the point where the light ray crosses it.
The change in direction of the light ray depends on how the speed of light changes. The change in the speed of light is related to the indices of refraction of the media involved. In mediums that have a greater index of refraction the speed of light is less. Imagine moving your hand through the air and then moving it through a body of water. It is more difficult to move your hand through the water, and thus your hand slows down if you are applying the same amount of force.
Similarly, light travels slower when moving through mediums that have higher indices of refraction. For a ray at a given incident angle, a large change in speed causes a large change in direction, and thus a large change in angle.
The incoming ray is called the incident ray and the outgoing ray the refracted ray, and the associated angles the incident angle and the refracted angle.
The second video discusses total internal reflection TIR in detail. Total internal reflection happens when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle.
Total internal reflection is a phenomenon that happens when a propagating wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the other side of the boundary and the incident angle is greater than the critical angle, the wave cannot pass through and is entirely reflected.
The critical angle is the angle of incidence above which the total internal reflectance occurs. What is Total Internal Reflection? The critical angle is the angle of incidence above which total internal reflection occurs. Consider a light ray passing from glass into air. The light emanating from the interface is bent towards the glass. When the incident angle is increased sufficiently, the transmitted angle in air reaches 90 degrees. It is at this point no light is transmitted into air.
Fig 1 : Refraction of light at the interface between two media, including total internal reflection. Total internal reflection is a powerful tool since it can be used to confine light. One of the most common applications of total internal reflection is in fibre optics. An optical fibre is a thin, transparent fibre, usually made of glass or plastic, for transmitting light. The construction of a single optical fibre is shown in.
Fig 2 : Fibers in bundles are clad by a material that has a lower index of refraction than the core to ensure total internal reflection, even when fibers are in contact with one another. This shows a single fiber with its cladding. The basic functional structure of an optical fiber consists of an outer protective cladding and an inner core through which light pulses travel. The difference in refractive index of the cladding and the core allows total internal reflection in the same way as happens at an air-water surface show in.
If light is incident on a cable end with an angle of incidence greater than the critical angle then the light will remain trapped inside the glass strand. In this way, light travels very quickly down the length of the cable over a very long distance tens of kilometers.
Optical fibers are commonly used in telecommunications, because information can be transported over long distances, with minimal loss of data. Another common use can be found in medicine in endoscopes. The field of applied science and engineering concerned with the design and application of optical fibers are called fiber optics.
When unpolarized light is incident at this angle, the light that is reflected from the surface is therefore perfectly polarized. This special angle of incidence is named after the Scottish physicist Sir David Brewster — The physical mechanism for this can be qualitatively understood from the manner in which electric dipoles in the media respond to p-polarized light whose electric field is polarized in the same plane as the incident ray and the surface normal.
One can imagine that light incident on the surface is absorbed, and then re-radiated by oscillating electric dipoles at the interface between the two media. The refracted light is emitted perpendicular to the direction of the dipole moment; no energy can be radiated in the direction of the dipole moment. When light hits a surface at a Brewster angle, reflected beam is linearly polarized. Polarized sunglasses use the same principle to reduce glare from the sun reflecting off horizontal surfaces such as water or road.
Fig 2 : Photograph taken of a window with a camera polarizer filter rotated to two different angles. In the picture at left, the polarizer is aligned with the polarization angle of the window reflection. Polarization Experience : A polarizing filter allows light of a particular plane of polarization to pass, but scatters the rest of the light.
When two polarizing filters are crossed, almost no light gets through. Some materials have molecules that rotate the plane of polarization of light. When one of these materials is placed between crossed polarizing filters, more light is allowed to pass through.
We see about six colors in a rainbow—red, orange, yellow, green, blue, and violet; sometimes indigo is listed, too.
These colors are associated with different wavelengths of light. White light, in particular, is a fairly uniform mixture of all visible wavelengths.
Sunlight, considered to be white, actually appears to be a bit yellow because of its mixture of wavelengths, but it does contain all visible wavelengths. The sequence of colors in rainbows is the same sequence as the colors plotted versus wavelength. What this implies is that white light is spread out according to wavelength in a rainbow. Dispersion is defined as the spreading of white light into its full spectrum of wavelengths.
More technically, dispersion occurs whenever there is a process that changes the direction of light in a manner that depends on wavelength. Dispersion, as a general phenomenon, can occur for any type of wave and always involves wavelength-dependent processes. Colors of a Rainbow : Even though rainbows are associated with seven colors, the rainbow is a continuous distribution of colors according to wavelengths.
Refraction is responsible for dispersion in rainbows and many other situations. The angle of refraction depends on the index of refraction, as we saw in the Law of Refraction. We know that the index of refraction n depends on the medium.
But for a given medium, n also depends on wavelength. Note that, for a given medium, n increases as wavelength decreases and is greatest for violet light. Thus violet light is bent more than red light and the light is dispersed into the same sequence of wavelengths. Pure Light and Light Dispersion : a A pure wavelength of light falls onto a prism and is refracted at both surfaces.
Since the index of refraction varies with wavelength, the angles of refraction vary with wavelength. A sequence of red to violet is produced, because the index of refraction increases steadily with decreasing wavelength. Rainbows are produced by a combination of refraction and reflection. You may have noticed that you see a rainbow only when you look away from the sun.
Light enters a drop of water and is reflected from the back of the drop.
A common Physics lab is to sight through the long side of an isosceles triangle at a pin or other object held behind the opposite face. When done so, an unusual observation - a discrepant event - is observed. The diagram on the left below depicts the physical situation. A ray of light entered the face of the triangular block at a right angle to the boundary. This ray of light passes across the boundary without refraction since it was incident along the normal recall the If I Were An Archer Fish page.
total internal icel3.org - Free download as Powerpoint Presentation .ppt /.pptx), PDF File WHEN THE ANGLE OF REFRACTION IS 90 0.
In this article, we shall study the phenomenon of total internal reflection and its applications. Total Internal Reflection of Light and its Explanation:. Let us consider a point source O in a denser medium Water. Let XY be the boundary separating the denser medium Water and the rarer medium Air.
A small part of the incident ray is reflected. For light traveling through a denser medium to a less dense medium, the angle of refraction,r in the less dense medium is larger than the angle of incidence,i in the denser medium. As the angle of incidence increases, the angle of refraction also increases. The angle of refraction reaches 90o before the angle on incidence does. At the instance, the refracted ray moves along the boundary.
Light does not escape as it travels along the fiber optics cable because it undergoes total internal reflection. Doctors using a fibroscope to investigate suspected lung cancer in a patient's bronchi airways. A fibroscope is a flexible fibre optic cable with a camera on the end,. If the ray is incident on surface BC, from which surface and at what angle will the ray leave the block?
Report Download. The students Understand the phenomena of total internal reflectionAppreciate the applications of total internal reflection in various fields Develop logical reasoning abilityAre Exposed to the use of Total Internal Reflection in modern communication systems. What is Refraction? Refraction is the bending of light at the surface of separation between two transparent media when light passes from one medium to anotherLight bends towards the normal when it travels from a rarer to denser mediumLight bends away from the normal when it travels from a denser to rarer medium. Consider a ray of light travelling from a denser to rarer mediumThe ray of light bends away from the normal in the rarer mediumDenser mediumRarer medium.
What happen if i is bigger than c? The light is reflected internal at the surface in a medium glass. Its known as Total Internal Reflection. Normal State two conditions for total internal reflection could occur. Prism: Observe the changes of the ray when the angle of incidence ray in prism is increased.
Eighth Grade Grade 8 Light and Optics questions for your custom printable tests and worksheets. They travel all the way to the lateral geniculate nucleus. Beautiful PPT theme featuring science - fiber optics close-up modern computer backdrop and a mint green colored foreground Colorful PPT layouts enhanced with high tech - bunch of optical fibres dinamic backdrop and a navy blue colored foreground. Atmospheric Optics is the fancy name for light and colour in the atmosphere, such as rainbows, halos, shadows, and mirages. This is typically performed as a two dimensional fast discrete transform.
Whenever you look into a mirror or squint at sunlight glinting off a lake, you are seeing a reflection. When you look at the text in a book, you are actually seeing the light that is reflected from it. Large telescopes use reflections to form images of stars and other astronomical objects. In fact, the only way we can see an object that does not itself emit light is if that object reflects light. The law of reflection is illustrated in, which also shows how the angles are measured relative to the perpendicular to the surface at the point where the light ray strikes.