O-LevelPhysicsLight5054/12 · May/June 2023 · Q211 Mark
The diagrams show light incident on the straight edge of a semi-circular glass block after passing through it. Which diagram shows refraction and an angle i equal to the critical angle of the glass? [Four diagrams (A, B, C, D), each showing a semi-circular glass block. In each, a ray enters the curved surface normally, passes to the straight surface, where it is incident at an angle 'i' to the normal. In diagram C, the refracted ray is shown grazing along the straight surface.]
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ADiagram A shows an incident ray from inside the glass at angle 'i' to the normal, partially reflecting and partially refracting out, with the refracted ray bent away from the normal.
BDiagram B shows an incident ray from inside the glass at angle 'i' to the normal, with the refracted ray exiting the block, bent away from the normal.
CDiagram C shows an incident ray from inside the glass at angle 'i' to the normal, with the refracted ray travelling along the boundary surface, indicating the critical angle.
DDiagram D shows an incident ray from inside the glass at angle 'i' to the normal, with the ray totally internally reflected back into the glass.
✓ Correct answer
C: Diagram C shows an incident ray from inside the glass at angle 'i' to the normal, with the refracted ray travelling along the boundary surface, indicating the critical angle.
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