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In diagram 1, total internal reflection occurs at Q - Edexcel - GCSE Physics - Question 3 - 2013 - Paper 1
Question 3
In diagram 1, total internal reflection occurs at Q. Explain why total internal reflection occurs at Q.
Worked Solution & Example Answer:In diagram 1, total internal reflection occurs at Q - Edexcel - GCSE Physics - Question 3 - 2013 - Paper 1
Step 1
Angle of incidence in glass greater than critical angle
Answer
Total internal reflection at point Q occurs because the angle of incidence of the light rays within the glass prism exceeds the critical angle for glass, which is approximately 42 degrees. When light attempts to pass from a denser medium (glass) to a less dense medium (air), if the angle of incidence is greater than the critical angle, the light cannot exit the glass and is instead reflected back into the prism.
Step 2
Refractive index comparison
Answer
In addition, glass has a higher refractive index than air. This means that light travels slower in glass compared to air. As a result, when the angle of incidence exceeds the critical angle, total internal reflection occurs, ensuring that all the light is reflected back within the glass prism rather than transmitted into the air.