| The refractive index (n) measures how much light slows down in a material compared to a vacuum, calculated as where c is the speed of light in a vacuum and c_s is the speed in the substance. | Refractive Index |
| How is the refractive index calculated? | n = c/c_s, where c is the speed of light in a vacuum and c_s is the speed in the substance. |
| A material with a higher refractive index is also known as being more optically dense. | Optical Density |
| What does a higher refractive index indicate about a material? | It indicates that the material is more optically dense. |
| The refractive index of air is approximately 1, since light does not slow down significantly in air compared to a vacuum. | Refractive Index of Air |
| What is the approximate refractive index of air? | Approximately 1. |
| Refraction occurs when a wave enters a different medium, causing it to change speed, wavelength and direction towards or away from the normal depending on the refractive indices. | Refraction |
| What happens to light during refraction? | It changes direction towards or away from the normal depending on the refractive indices. |
| Snell’s Law relates the angles of incidence and refraction to the refractive indices of | Snell’s Law |
| What is the formula for Snell’s Law? | n_1sinθ_1 = n_2sinθ_2. |
| In Snell’s Law: n1 is the refractive index of material 1 n2 is the refractive index of material 2 θ1 is the angle of incidence in material 1 θ2 is the angle of refraction in material 2 | Snell’s Law Variables |
| What do the variables in Snell’s Law represent? | n1 is the refractive index of material 1,
n2 is the refractive index of material 2,
θ1 is the angle of incidence in material 1,
θ2 is the angle of refraction in material 2. |
| As light crosses the boundary between two materials, its speed changes, causing its direction to change due to refraction. | Change in Speed and Direction of Light |
| What causes light to change direction when it crosses the boundary between two materials? | The change in speed causes its direction to change due to refraction. |
| If n2 is more optically dense than n1, the light slows down and bends towards the normal. | Bending Towards the Normal |
| If n2 is less optically dense than n1, the light will bend away from the normal. | Bending Away from the Normal |
| What happens to light when n2 is less optically dense than n1? | The light bends away from the normal. |
| The critical angle is the angle of incidence at which the angle of refraction becomes 90° and the light is refracted along the boundary. | Critical Angle (θc) |
| What is the critical angle? | It is the angle of incidence where the angle of refraction is 90°, and the light refracts along the boundary. |
| The critical angle can be found using the formula where n1 is greater than n2. | Formula for Critical Angle |
| What is the formula for calculating the critical angle? | sinθ_c = n2/n1, where n1 > n2. |
| Total internal reflection occurs when the angle of incidence is greater than the critical angle, and the refractive index of the incident material (n1) is greater than the refractive index at the boundary (n2). | Total Internal Reflection (TIR) |
| When does total internal reflection (TIR) occur? | When the angle of incidence is greater than the critical angle and n1 is greater than n2. |
| Optical fibres are thin, flexible tubes of plastic or glass that carry light signals, using total internal reflection to transmit information. | Optical Fibres |
| What are optical fibres? | Thin, flexible tubes of plastic or glass that carry information in the form of light signals using total internal reflection. |
| Optical fibres have a core that is optically dense and surrounded by cladding with a lower optical density to allow TIR and protect the core from damage. | Core and Cladding in Optical Fibres |
| What is the function of the cladding in optical fibre? | It allows total internal reflection and protects the core from damage and signal degradation. |
| Absorption occurs when part of the signal's energy is absorbed by the fibre, reducing the amplitude of the signal and potentially leading to a loss of information. | Absorption (Signal Degradation) |
| What happens during absorption in optical fibres? | Part of the signal's energy is absorbed, reducing the signal's amplitude and potentially leading to a loss of information. |
| Dispersion causes pulse broadening, where the received signal is broader than the original, and overlapping signals may cause information loss. | Dispersion (Pulse Broadening) |
| What is pulse broadening and how does it affect signal transmission? | Pulse broadening is when the received signal becomes broader than the original, leading to potential overlap and loss of information. |
| Modal dispersion is caused by light rays entering the fibre at different angles, resulting in different path lengths and travel times, which leads to pulse broadening. | Modal Dispersion |
| How does modal dispersion cause pulse broadening? | Light rays take different paths and times through the fibre, leading to pulse broadening. |
| Modal dispersion can be reduced by making the core narrower, which minimizes the difference in path lengths. | Reducing Modal Dispersion |
| How can modal dispersion be reduced? | By making the core narrower, reducing the difference in path lengths. |
| Material dispersion occurs when light of different wavelengths travels at different speeds through the fibre, causing pulse broadening. | Material Dispersion |
| What causes material dispersion in optical fibres? | Light of different wavelengths travels at different speeds, leading to pulse broadening. |
| Material dispersion can be reduced by using monochromatic light, which has a single wavelength. | Reducing Material Dispersion |
| How can material dispersion be prevented? | By using monochromatic light with a single wavelength. |
| An optical fibre repeater regenerates the signal, reducing absorption and dispersion during transmission. | Optical Fibre Repeater |
| How can absorption and dispersion be reduced in long-distance signal transmission? | By using an optical fibre repeater to regenerate the signal. |
