Optics Practical Test – Unit 8 – Mark Scheme
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Draw the outline of the transparent block with your pencil……………………………………………………………………………… (1)
Mark and draw a point near the middle of the upper face of the outline…………………………………………………………. (1)
Use a protractor to measure and draw a perpendicular line starting from that point………………………………………. (1)
Label the perpendicular line with the name normal…………………………………………………………………………………………. (1)
Make light incident into the acrylic block at the point that you drew before……………………………………………………. (1)
Mark and draw the point at which light leaves the lower face of the block………………………………………………………. (1)
Remove the acrylic block, extend your normal line, and connect the upper point
to the lower point by tracing a straight line……………………………………………………………………………………………………… (1)
Measure both incident and refracted angles by using a protractor…………………………………………………………………… (1)
Use Snell’s law to calculate index of refraction…………………………………………………………………………………………………. (1)
Calculate sines correctly…………………………………………………………………………………………………………………………………… (1)
Final result with 2 or 3 s.f. within range 1.4 – 1.6 …………………………………………………………………………………………….. (1)
Speed of light calculated correctly……………………………………………………………………………………………………………………. (2)
Frequency calculated correctly…………………………………………………………………………………………………………………………. (3)
Statement NO (1) valid justification………………………………………………………………………………………………………………… (1)
Right calculation of critical angle………………………………………………………………………………………………………………………. (2)
Name as total internal reflection (1) + optical fibers (1)……………………………………………………………………………………..(2)
Total: [21 marks]