Tag Archives: total internal reflection
Light Experiments – Glass Block and Pins
The video include 3 different light experiments which involve glass block and pins.
Most students faced difficulties in locating the pins through the glass block. It is important to close one eye and use your master eye to view.
Hope this video helps!
In experiments like this, the sources of error include:
– the holes created by the pins are too big, hence the line drawn using the two holes may not be very precise, hence affecting the distance/angle measured (depends on experiments)
– When putting back the glass block back on the paper, the position may be not exactly the same, hence affecting the angle/distance measured.
As a precaution, it is good to ensure that the distance between the two pins are more than 4 – 5 cm. With the holes further apart, the line drawn will be more accurate.
Critical Angle
Demonstration of Reflection, Refraction and TIR using light source with a slit
Reflection of light using a mirror
Refraction of light using various shaped optical mediums
Total Internal Reflection (TIR) using a semi-circular perspex
For Total Internal Reflection (TIR) to occur:
1) angle of incidence i is greater than the critical angle c
2) the light is travelling from an optically denser medium towards a less dense medium
What is Total Internal Reflection (TIR)?
Overview of Total Internal Reflection (TIR)
Explanation of the various stages:
Total Internal Reflection (TIR) example 02
Solutions:
a) 38.8o    b) 41.8o
c) 51.2o . The ray does not emerge as total internal reflection has occurred. The angle of incidence is greater than critical angle and the light is traveling from a denser towards a less dense medium.
Click here to view the video tutorial for working and explanation for (a) and (b).
Click here to view the video tutorial for working and explanation for (c) and (d).
Total Internal Reflection (TIR) example 01
Solutions:
a) Refraction   b) 48.6o   c) c = 41.8o   e) 70o
d) Total internal reflection has occured, as the angle of incidence is greater than critical angle and the light is traveling from a denser medium (glass) towards a less dense medium (air)
Click on the video tutorial for explanation and working for part (a) and (b).
Click on the video tutorial for explanation and working for part (c) to (e).
Total Internal Reflection (TIR)
For total internal reflection (TIR) to occur,
1) angle of incidence (i) > critical angle (c)
2) light is traveling from a denser medium towards a less dense medium
An example of Total Internal Reflection
Some designer lightings like that one show in the video make use of total internal reflection. This was taken at Spring Maternity @NEX Jul 2011.
An Example of Total Internal Reflection from evantoh on Vimeo.
Each strand is actually make of transparent plastic-like material, which is flexible and has higher optical density than the air.
Recall the 2 conditions for total internal reflection to take place
1: light is traveling from denser medium (plastic) to the less dense medium (air)
2: angle of incidence is greater than critical angle
Hence from the centre light source, light can total internal reflection and comes out from the other end of each strand. There you have it! A unique designer lighting, just making use of physics!
Sent from my iPad
Evan's Space 