Light Waves
4 marks · NormalDescribe an experiment to determine the refractive index of a glass block using a ray box and a protractor.
List the apparatus you would need.
Outline the steps you would take during the experiment.
State how you would use your results to calculate the refractive index.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) Ray box, glass block, paper, protractor, pencil, ruler.
(b) Draw around the glass block on paper. Shine a ray at a known angle of incidence to one face. Mark the incident and refracted rays. Measure the angles with a protractor. Repeat for several angles of incidence.
(c) Calculate the refractive index using n = sin i / sin r for each pair of angles, then take the average value.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States apparatus: ray box, glass block, protractor, paper, pencil, ruler.
M1 (b) · 1 mark · Describes procedure: draw around block, shine ray, mark incident and refracted rays.
M2 (b) · 1 mark · Mentions measuring angles and repeating for different incidences.
A1 (c) · 1 mark · States use of n = sin i / sin r to calculate refractive index from results. (follow-through)
Worked solution
a) Apparatus: ray box, glass block, paper, ruler, pencil, protractor. b) Steps: - Place the glass block on paper and trace its outline. - Shine a ray from the ray box at a known angle of incidence to an edge of the block. - Mark the incident and refracted rays on the paper. - Remove the block and draw in the normal. Measure angles of incidence and refraction with the protractor. - Repeat for several different angles of incidence. c) For each pair of angles, use the formula n = sin i / sin r. Average the results for greater accuracy.