Unit 10 · Effects of injuries to the cornea in the eyes
Total Internal Reflection of Light
ScienceSubject
8 minEstimated read
Activity 10.5
Refraction of light while passing from denser to the rarer medium by making different angles of incidence
Method
Take a semicircular glass slab, a laser beam pointer or ray box, and a protractor.
On a plain sheet of paper, draw two lines as if they were the two axes of a graph.
Prepare a scale for measuring the angles, with the centre of the protractor as the origin O and the reference line parallel to the x-axis.
Place the semicircular glass slab on the sheet so that its centre lies at O and its flat edge is parallel to the x-axis.
Pass the laser beam into the glass so that it is perpendicular to the semicircular surface.
Measure the angle of incidence (i) and the angle of refraction (r) at O and fill in the table.
Keep on increasing the angle of incidence. Note down the angle at which the refracted ray becomes parallel to the glass-air interface, making an angle of 90° with the normal.
Angle of incidence
Angle of refraction/angle of reflection
Result: refraction of light/reflection of light
30°
Refraction of light
35°
90°
Refraction of light
50°
Discussion
In which medium does the light go if the angle of incidence is increased after the angle of refraction has become 90°?
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