Optics
Experiment 3
Total Internal Reflection
Aim: To investigate total internal reflection and to measure the critical angle.
Apparatus: Semicircular glass block, ray-box with a single slit, protractor sheet.
Diagram:
Method:
Place the semicircular block on the protractor sheet and point the incident ray towards the center
of block.
Shine the ray of light toward the normal.
Move the ray-box around the glass-block until the incident ray is refracted out of the block at an
angle less than 90. Measure the angle of incidence and record it.
Move the ray-box around the block of glass till the refracted ray grazed just along the surface.
Measure the critical angle of glass and record it.
Move the ray-box around the block of glass until you observe total internal reflection. Measure
the angle of incidence and the angle of reflection and record them.
Results
Experiment 1: Angle of incidence =___________ , Angle of refraction =___________ .
Experiment 2: Critical angle =__________ , Angle of refraction =____________ .
Experiment 3: Angle of Incidence = _________, Angle of reflection = _______
V. Calleja
Optics
Experiment 3
Precautions:
The ray must graze the surface of the block at _________.
The experiment was performed in a _________________ to obtain more clear observations.
Conclusion:
When the angle of incidence was smaller than the critical angle the ray was __________out of
the glass block. At the ____________ angle the ray just grazed the surface. Beyond the critical
angle the ray was ____________________inside the glass block.
V. Calleja