SimReal: Physics - Light - Refraction 02 UiA Logo


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In the simulation window you see two points (red) A og B and a river (blue).
Imagine you are going from A to B running with a constant speed at land, swimming with a constant lower speed in the river and then running again from the river to the point B.
Question 1: In what direction should you run from A, where should you start your swimming trip, and where should you end your swimming trip before running to the point B to move from A to B in shortest possible time?
Question 2: Where should you build a cable line if it's more expensive to build in water than on land?

The correct answer of the question gives you the solution of the trajectory a light beam will follow going from A, refracting at the edge of the river (now a glass), travelling through the glass, refracting at the edge of the glasses again and ending at B. The light always follows the trajectory that gives the shortest possible travel time.

Move the sliders (touch points) on the edgres of the river and control the travelling time.
Find the minimum travelling time, measure and try to find out (by the toolbox at the bottom in the simulation window) a relation between the the angle of incidence and the angle of reflection at the horizontal line.

Compare your result by Snell's Law of Refraction: n1*sin(u1) = n2*sin(u2) where u1 and u2 are the angle of incidence and angle of refraction.
n1 and n2 are the refraction index (here for vacuum and glass for example).
The refraction index of an object is inversely proportional to the velocity of light in that object.

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