Chapters
Are you curious about total internal reflection and its remarkable applications in various optical devices and systems? If yes, prepare as we dig deeper into this concept in this insightful article. This article will illuminate the extraordinary uses and implications of total internal reflection from the intricate workings of fibre optics, enabling high-speed communication, to the mesmerizing behaviour of prisms, revealing a colourful spectrum of light. So, fasten your seatbelts as we embark on an enlightening journey through the wonders of this optical phenomenon.
Total Internal Reflection
When light travels from a heavy substance to a lighter one, it usually changes direction. But sometimes, instead of changing direction, all of the light bounces back. This is called total internal reflection.
It happens when the angle at which the light hits the surface is more significant than a specific angle, and the material it hits first is denser than the material it enters. So, for total internal reflection to occur, two things must be true: the angle at which the light hits the surface must be more significant than a certain angle, and the first material it encounters must be heavier than the second material.
Applications of Total Internal Reflection
Total internal reflection is essential in various applications, such as optical fibres and prisms.
1. Optical Fibres
Optical fibres are thin strands of high-quality glass that utilize total internal reflection to guide and contain light. They have various applications:
- Fibre broadband internet: Information is transmitted as light pulses through underground optical fibres, enabling high-speed internet connections.
- Medical endoscopes: Doctors use long tubes with optical fibres to visualize internal body parts by guiding light inside the patient and reflecting it to create an image.
- Decorations: Optical fibres are employed in decorations, such as artificial Christmas trees, to carry and distribute coloured light, creating dynamic visual effects.
Due to total internal reflection properties, the glass fibres absorb very little light. Light entering one end undergoes continuous internal review, even when the thread is bent, and emerges at the other end with minimal loss in brightness.
Optical fibres provide a unique and efficient means of transmitting various forms of information, including computer data, telephone calls, and video signals. These forms of communication can be converted into pulses of visible light or infrared light, allowing them to travel long distances through optical fibres.
Advantages of using optical fibres for long-distance communication
The use of optical fibres for long-distance communication offers several benefits. It is a cost-effective solution compared to traditional copper wires required for electrical signal transmission. Glass fibres used in optical cables are more economical than copper wires.
Furthermore, optical fibres have a much higher information-carrying capacity than copper cables of the same diameter. This means optical fibres can handle and transmit significantly more critical data, facilitating faster and more efficient communication channels.
Endoscopes
Endoscopes, equipped with optical fibres, play a vital role in enabling surgeons to visualize and examine the internal regions of patients. Within the endoscope, a bundle of optical fibres is enclosed in a tube, which guides light into the patient and collects the reflected light to form an image.
Surgeons can observe real-time visuals of the patient's internal organs and tissues by connecting the endoscope to a monitor. Optical fibres contribute to the feasibility of keyhole surgery, as the endoscope incorporates instruments for cutting and retrieving tissue.
The advantages of endoscopic procedures are significant. They eliminate the need for extensive incisions, resulting in reduced scarring, quicker recovery times, and decreased postoperative pain for the patients. Optical fibres benefit by facilitating minimally invasive surgeries that enhance patient outcomes.
2. Prisms
Prisms are utilized in optical instruments, including periscopes, binoculars, telescopes, and cameras. They help redirect and manipulate light for better viewing and imaging.
For example, a periscope is a handy device that lets you see tall objects without directly exposing yourself. It consists of two prisms arranged at right angles, which utilize total internal reflection to reflect and redirect the light from above, allowing you to see the objects from a higher vantage point.
Example
The following diagram shows a ray of red light path through a glass prism.
Answer the following by observing the diagram above:
1)Which process is happening to the ray at point X?
2) No light is coming out of the prism at point Y. Which process is happening to the light at this point?
3) Explain how the Speed of light changes as it passes through points Y and Z?
Solution
1) Process happening to the ray at point X
The ray of red light bends when it enters the glass prism. This bending is called refraction. It happens because the light is moving from one material to another.
2) Process happening to the ray at point Y
At point Y, the light doesn't come out of the prism. This is because the angle at which the light hits the boundary of the prism is too big. It's called the critical angle. Instead of coming out, the sunlight reflects inside the prism. This is called total internal reflection.
3a) Speed of light at point Y
When the light undergoes total internal reflection at point Y, its Speed remains unchanged. A comprehensive internal review doesn't affect how fast the light travels.
3b) Speed of light at point Z
Its speed changes as the light passes point Z and leaves the prism. It slows down when it enters the prism because the glass is denser. Then, when it comes out of the prism and enters the less thick air, it speeds up again. The change in Speed happens because different materials affect how fast light can travel through them.
Critical Angle
When we increase the angle at which light hits a surface, i.e. the angle of incidence, the angle at which it bends or changes direction, i.e. the angle of refraction, also increases until it approaches 90 degrees. When the angle of incidence reaches precisely 90 degrees, the light refracts along the boundary. At this specific point, the rise of incidence is called the critical angle, often denoted as "c."
When light travels from one medium to another, there comes a point where if the angle at which it enters the second medium is too steep, the light completely bounces back instead of bending. This phenomenon is called total internal reflection. It happens when the angle of incidence is more significant than a specific angle, known as the critical angle. In total internal reflection, the light ray doesn't pass through but reflects into the original medium.
Relationship Between Critical Angle and Refractive Index
The critical angle, denoted as c, is determined by the refractive index of a material, represented by the symbol n. The relationship between these two quantities can be expressed through the following equation:
We can rearrange the above equation to calculate the refractive index, n:
By examining this equation, we can observe an interesting relationship:
- When the refractive index of a material is more extensive, the critical angle becomes smaller. This implies that light rays are more likely to undergo total internal reflection in materials with a higher refractive index.
- In other words, when light travels through a substance with a higher refractive index, it has a greater tendency to bounce back and remain within the material rather than pass through it.
Did you like this article? Rate it!
Loading...
You are the best,, coz you have gotten content about the topics
Hello ! Glad to hear that you’ve found the content useful!