Flashcards in Total Internal Reflection Deck (18):
The complete reflection of a light ray reaching an interface with a less dense medium when the angle of incidence exceeds the critcial angle .
What happens when light travels from one medium to another ?
Changes speed and refracted .
What happens when light rays are travelling from a less dense material to a dense medium ?
They are refracted towards the normal .
What happoens from a dense material such as glass to a less dense air medium ?
They are refracted away from the normal .
When does total internal reflection occur ?
It occurs when light must travel from a dense medium to a less does medium
What is the critical angel ?
The angle of incidence beyond the rays of lighting passing through a dense medium to the surface of a less dense medium are no longer refracted but totally reflected .
Angle of incidence less than the critical angle
When the angle of incidence of light ray leaving the glass is less dense tan the critical angle , light ray speeds up on leaving the glass refracted away from the normal .
Angle of incidence is equal to the critical angle .
When the angle of incidence of light ray reaches the critical angle 42 degrees the angle of refraction is 90 degrees .The refracted ray travels along the surface of the denser medium of glass.
Angle of incidence greater than the critical angle .
When the angle of incidence of light ray is grater than the critical angle no refraction occurs all light is reflected back into the denser materials in this case glass and this called total internal reflection
What are the two conditions for total internal reflection to occur ?
The rays of light must travel from a dense medium to a less dense medium
Angle of incidence must be greater than the crtiical angel .
What happens when light travels from a high index materiel to a low index ?
It bends a away from the normal .
What happens if you increase the angle of incidence ?
The angle of refraction will increase because they are the same .
Calculation in critical angle
review book revision physics ./excercise.
Calculate the refractive index for this material if the critical angle is 43.8 degrees
Critical angle =43.8 degrees
SinC=1 divided by n
N= 1 divided by 0.692
Explain why there is total internal reflection in optical fibres
Fibre optical cable denser than outside/air so this means the incidence /boundary reflection is greater than critical angle .
Have a higher refractive index but is surrounded by cladding which gives it a lower refractive index .
Why does light go faster in vacuum but slower in other materials .
Because its interacts with particles in them . The more optically dense a material is the more light slows down .