Science
Task B: Gather Secondary Data
Part 1
Collect relevant information on explaining what is internal reflection.
Report Sheet 1 - What is Internal Reflection?
Source 1) Encyclopaedia Britannica
Information from Source 1
Total internal reflection, in physics, complete reflection of a ray of light within a medium such as water or glass from the surrounding surfaces back into the medium. The phenomenon occurs if the angle of incidence is greater than a certain limiting angle, called the critical angle. In general, total internal reflection takes place at the boundary between two transparent media when a ray of light in a medium of higher index of refraction approaches the other medium at an angle of incidence greater than the critical angle. For a water-air surface the critical angle is 48.5°. Because indices of refraction depend on wavelength, the critical angle (and hence the angle of total internal reflection) will vary slightly with wavelength and, therefore, with colour. At all angles less than the critical angle, both refraction and reflection occur in varying proportions.
Glass prisms can be shaped to produce total internal reflection and as such are employed in binoculars, periscopes, telescopes, and other optical instruments. Light rays may be conducted over long, twisting paths by multiple total internal reflection in glass or plastic rods or fibres. See also fibre optics.
Keywords from Source 1
Reflection, ray of light, medium, angle of incidence, critical angle, two transparent media, index of refraction, refraction, total internal refraction, boundary
Summarize in your own words
In a medium of a higher refractive index, total internal reflection occurs at the boundary of two transparent media as the ray of light approaches the other medium of a lower refractive index, when the angle of incidence is greater than the critical angle.
Part 2
Collect two relevant sources of information that explains how internal reflection is used in everyday life.
Report sheet 2 - How internal reflection is used in everyday life Diamonds
Source 2) http://www.cyberphysics.co.uk/topics/light/TIR.htm
Information from Source 2
Diamonds
From glass to air the critical angle is about 42o but it varies from one medium to another. The material that gives the smallest critical angle is diamond. That is why they sparkle so much! Rays of light can easily be made to 'bounce around inside them' by careful cutting of the stone and the refraction at the surfaces splits the light into a spectrum of colours!
Keywords from Source 2
medium, material, critical angle, sparkle, rays of light, cut, refraction, spectrum, boundary
Summarize in your own words
Internal reflection occurs in diamonds, with diamonds having the smallest critical angle. The boundary between the high refractive index of the diamond medium and the low refractive index of the air is extremely small. By having the cut of the diamond precise, the rays of light both reflect internally and refract at different surfaces, splitting the light into a spectrum of colours. The enhancement of the sparkle depends on the strategy of the cut.
Report sheet 3 - How internal reflection is used in everyday life Optical fibers
Source 3) http://www.cyberphysics.co.uk/topics/light/FiberOptics/FibreOptics.htm
Information from Source 3
Optical Fiber
In the medium of a higher refractive index, total internal reflection occurs at the boundary of two transparent media as the ray of light approaches the other medium of a lower refractive index, when the angle of incidence is greater than the critical angle.
Internal reflection occurs in diamonds, with diamonds having the smallest critical angle. The boundary between the high refractive index of the diamond medium and the low refractive index of the air is extremely small. By having the cut of the diamond precise, the rays of light both reflect internally and refract at different surfaces, splitting the light into a spectrum of colours. The enhancement of the sparkle depends on the strategy of the cut.
Total internal reflection occurs in optical fibres. They are thin, transparent fibres, often made from glass and plastic. Inside the fibres, light with an angle of incidence greater than the critical angle travels quickly by bouncing/reflecting from the cladding (which has a low refractive index) to the core (which has a high refractive index) and back again, internally reflecting along the core until it reaches its source, covering long distances. Telecommunications use optical fibres to transfer information over longer distances.
One example of internal reflection in everyday life is diamonds. Internal reflection occurs in diamonds, with diamonds having the smallest critical angle. The boundary between the high refractive index of the diamond medium and the low refractive index of the air is extremely small. By having the cut of the diamond precise, the rays of light both reflect internally and refract at different surfaces, splitting the light into a spectrum of colours. The enhancement of the sparkle depends on the strategy of the cut, and that can be one of diamonds advantages and disadvantages. The disadvantage to this is that it requires a level of skill and preciseness and if the cut is off, the light will be reflected poorly. In addition, once the diamond is chipped in any way, the quality of the produced reflection will be defected and may cause harm. The advantage to diamonds is the beauty it produces as this material is worn as jewelry.
Another example of of internal reflection in everyday life is optical fibres. Total internal reflection occurs in optical fibres. They are thin, transparent fibres, often made from glass and plastic. Inside the fibres, light with an angle of incidence greater than the critical angle travels quickly by bouncing/reflecting from the cladding (which has a low refractive index) to the core (which has a high refractive index) and back again, internally reflecting along the core until it reaches its source, covering long distances. Telecommunications is an example of internal reflection that uses optical fibres to transfer information over longer distances. Covering long distances is one of optical fibres advantages, with minimal loss of data along the way and the speed at which that information travels at. Although, there is a disadvantage to optical fibres. Optical fibres are fragile and are vulnerable to damage because they are usually made out of glass. The cables can only be twisted so far before the cladding is damaged and light can no longer be emitted through it.
Report sheet 2 - How internal reflection is used in everyday life Diamonds
Source 2) http://www.cyberphysics.co.uk/topics/light/TIR.htm
Information from Source 2
Diamonds
From glass to air the critical angle is about 42o but it varies from one medium to another. The material that gives the smallest critical angle is diamond. That is why they sparkle so much! Rays of light can easily be made to 'bounce around inside them' by careful cutting of the stone and the refraction at the surfaces splits the light into a spectrum of colours!
Relatively speaking, the critical angle 24.4o for the diamond-air boundary is extremely small. This property of the diamond-air boundary plays an important role in the brilliance of a diamond gemstone. Having a small critical angle, light has the tendency to become "trapped" inside of a diamond once it enters. Most rays approach the diamond at angles of incidence greater than the critical angle (as it is so small) so a light ray will typically undergo TIR several times before finally refracting out of the diamond. This gives diamond a tendency to sparkle. The effect can be enhanced by the cutting of a diamond gemstone with a 'strategically' planned shape. The diagram to the left depicts the total internal reflection within a diamond gemstone with a 'strategic' and a 'non-strategic' cut.
medium, material, critical angle, sparkle, rays of light, cut, refraction, spectrum, boundary
Summarize in your own words
Internal reflection occurs in diamonds, with diamonds having the smallest critical angle. The boundary between the high refractive index of the diamond medium and the low refractive index of the air is extremely small. By having the cut of the diamond precise, the rays of light both reflect internally and refract at different surfaces, splitting the light into a spectrum of colours. The enhancement of the sparkle depends on the strategy of the cut.
Report sheet 3 - How internal reflection is used in everyday life Optical fibers
Source 3) http://www.cyberphysics.co.uk/topics/light/FiberOptics/FibreOptics.htm
Information from Source 3
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 overall diameter of the fiber is about 125 μm and that of the core is just about 50 μm. 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.
Keywords from Source 3
Total internal reflection, fibre optics, transparent fibre, light, cladding, core, angle of incidence, critical angle, travel, information
Summarize in your own words
Total internal reflection occurs in optical fibres. They are thin, transparent fibres, often made from glass and plastic. Inside the fibres, light with an angle of incidence greater than the critical angle travels quickly by bouncing/reflecting from the cladding (which has a low refractive index) to the core (which has a high refractive index) and back again, internally reflecting along the core until it reaches its source, covering long distances. Telecommunications use optical fibres to transfer information over longer distances.
Summary of Information
Q. What is Internal Reflection and how do we use it in everyday life?In the medium of a higher refractive index, total internal reflection occurs at the boundary of two transparent media as the ray of light approaches the other medium of a lower refractive index, when the angle of incidence is greater than the critical angle.
Internal reflection occurs in diamonds, with diamonds having the smallest critical angle. The boundary between the high refractive index of the diamond medium and the low refractive index of the air is extremely small. By having the cut of the diamond precise, the rays of light both reflect internally and refract at different surfaces, splitting the light into a spectrum of colours. The enhancement of the sparkle depends on the strategy of the cut.
Total internal reflection occurs in optical fibres. They are thin, transparent fibres, often made from glass and plastic. Inside the fibres, light with an angle of incidence greater than the critical angle travels quickly by bouncing/reflecting from the cladding (which has a low refractive index) to the core (which has a high refractive index) and back again, internally reflecting along the core until it reaches its source, covering long distances. Telecommunications use optical fibres to transfer information over longer distances.
Task C: Written Report
If a medium can emit light, then it has a refractive index. Depending on the medium, it also determines the light ray's speed. Air, gasses, water, etc., have low refractive indexes and are mediums with low density, meaning that light travels quickly through it. Glass, plastic, diamond etc., have high refractive indexes and are mediums with a thicker density, meaning that light travels slowly though it.
Refraction occurs when an incident ray travels quickly through a less dense medium and once hitting the boundary of a more denser medium, the light travels slowly through it, changing its speed and direction. The light will then bend towards the normal line. Once the light ray leaves the boundary of the denser medium, the ray of light speeds up again, changing its direction and speed, traveling quickly again through the less dense medium. The ray leaving the denser medium is called the refractive ray.
In a medium of a higher refractive index, total internal reflection occurs at the boundary of two transparent media as the ray of light approaches the other medium of a lower refractive index. When the angle of incidence is greater than the critical angle, it will reflect rather than refract. All that needs to be changed to reflect rather than refract is the increase of the angle of incidence.
Refraction occurs when an incident ray travels quickly through a less dense medium and once hitting the boundary of a more denser medium, the light travels slowly through it, changing its speed and direction. The light will then bend towards the normal line. Once the light ray leaves the boundary of the denser medium, the ray of light speeds up again, changing its direction and speed, traveling quickly again through the less dense medium. The ray leaving the denser medium is called the refractive ray.
In a medium of a higher refractive index, total internal reflection occurs at the boundary of two transparent media as the ray of light approaches the other medium of a lower refractive index. When the angle of incidence is greater than the critical angle, it will reflect rather than refract. All that needs to be changed to reflect rather than refract is the increase of the angle of incidence.
One example of internal reflection in everyday life is diamonds. Internal reflection occurs in diamonds, with diamonds having the smallest critical angle. The boundary between the high refractive index of the diamond medium and the low refractive index of the air is extremely small. By having the cut of the diamond precise, the rays of light both reflect internally and refract at different surfaces, splitting the light into a spectrum of colours. The enhancement of the sparkle depends on the strategy of the cut, and that can be one of diamonds advantages and disadvantages. The disadvantage to this is that it requires a level of skill and preciseness and if the cut is off, the light will be reflected poorly. In addition, once the diamond is chipped in any way, the quality of the produced reflection will be defected and may cause harm. The advantage to diamonds is the beauty it produces as this material is worn as jewelry.
Another example of of internal reflection in everyday life is optical fibres. Total internal reflection occurs in optical fibres. They are thin, transparent fibres, often made from glass and plastic. Inside the fibres, light with an angle of incidence greater than the critical angle travels quickly by bouncing/reflecting from the cladding (which has a low refractive index) to the core (which has a high refractive index) and back again, internally reflecting along the core until it reaches its source, covering long distances. Telecommunications is an example of internal reflection that uses optical fibres to transfer information over longer distances. Covering long distances is one of optical fibres advantages, with minimal loss of data along the way and the speed at which that information travels at. Although, there is a disadvantage to optical fibres. Optical fibres are fragile and are vulnerable to damage because they are usually made out of glass. The cables can only be twisted so far before the cladding is damaged and light can no longer be emitted through it.
