idea by J. Blum, Christliche Deutsche Schule Chiang Mai
Even named after the Dutch astronomer Willebrord Snellius, Snell's Law was first discribed in 984. To examine refraction you will need a light source with a beam, a prism and a possibility to messure different angles (triangle ruler).
|incident angle α||10 °||20 °||30 °||40 °||50 °||60 °||70 °||80 °||90 °|
|refracted angle β|
|sin α/sin β|
As a reference you will get one value.
|incident angle α||30 °|
|refracted angle β||20|
|sin α/sin β||1.46|
Construct the ray profile
Inside a pond is a fish.
Fermat's principle states, that light takes the fastets path. If it is reflected on a mirror, the reflection law states that the incident angle must be similar to the reflected angle of light. But right there the path of light reaches its shortes and fastest way. So Pierre de Fermat had an interessting point of view..
Just take a 10 m rope and imagine the following situation: You are at point A. Before you come to point B you must get water from the riverside of Nil. But you would like to take shortes and thus fastest way.
Fermat's principle states that light travels the fastest way. Up to now it was even the shortest. No it will be different, since travelling throug water light will be slowed down.
Try to act these situation. Going through water means just having at least half the speed as on lawn.
Here are some statements of students:
Interested in more interactie experimente?
M. Kramer, "Physik als Abenteuer", Band 1, Aulis Verlag 2011
Optical fibres lead light over kilometers since the losses are very small and the speed to transport information is incredible fast. But first you have to get the ray of a laser into the optical fibre. Since the crital angle of this fibre is γ = 76 °, the angle α of the incident ray is restricted.
Little raindrops in the alpes do refract and reflect the light. That is why the sun must be behind you and the rain in front of you, in order to see any rainbow.
|refraction of light||light changes its direction in a different medium, since it is slowed down|
|reflection of light||light is thrown back in a certain angle|
|refractive index $n$||ratio of speed of light in vacuum and a medium|
|speed of light $c$||the speed of light in air or vaccum is $c=300 \cdot 10^6\:m/s$|
|critical angle||the angle when light is not anymore refracted by its transition from a denser medium to a less dense medium|
|dispersion||wavelength dependent refraction|