A student template for investigating the refraction of light through a transparent rectangular block is prepared on a sheet of paper.
The student draws the outline of the block ABCDABCDABCD. A normal NN′ NN'\,NN′ is drawn passing through the top side AB AB\,AB at point F F\,F and the bottom side CD CD\,CD at point GGG. An incident ray path EF EF\,EF is drawn at an angle of incidence i=30∘i = 30^\circi=30∘ to the normal.
After placing the block, the student places two pins P1 P_1\,P1 and P2 P_2\,P2 on the line EFEFEF. Looking through the opposite side CD CD\,CD of the block, she aligns two more pins P3 P_3\,P3 and P4 P_4\,P4 with the images of P1 P_1\,P1 and P2P_2P2.
She then removes the block, draws a straight line through the positions of P4 P_4\,P4 and P3 P_3\,P3 and extends it to meet the side CD CD\,CD at point HHH. Finally, she draws the line HFHFHF.
The student measures the length a a\,a of the line GH GH\,GH to be 14 mm and the length b b\,b of the line HF HF\,HF to be 42 mm.
Calculate the refractive index n n\,n of the material of the block using the equation:
n=b2a n = \frac{b}{2a} n=2abSuggest how far apart the student should place the pins P3 P_3\,P3 and P4 P_4\,P4 on the ray trace sheet.
State a reason for your suggestion in (b)(i).
The experiment can also be carried out using a ray of light produced by a ray box instead of using optical pins.
Assuming both methods are performed carefully: Suggest one source of inaccuracy when using the optical pin method.
Suggest one source of inaccuracy when using the ray box method.
100 exam-style questions on CIE IGCSE Physics 3.2.2 Refraction of light. Each one has a worked solution and a mark scheme showing where the marks go.