A student is investigating the refraction of light passing through a rectangular block of transparent material. The student first draws the outline of the block ABCD ABCD\,ABCD on a ray-trace sheet. They draw a normal to the side AB AB\,AB at point EEE, then draw an incident line FE FE\,FE at an angle of incidence i1=35∘i_1 = 35^\circi1=35∘ to the normal.
The student places two pins, P1 P_1\,P1 and P2P_2P2, on the line FEFEFE. Explain why the pins P1 P_1\,P1 and P2 P_2\,P2 should be placed as far apart as possible (at least 5.0 cm apart).
The student views the pins through the opposite face, CDCDCD, and places pins P3 P_3\,P3 and P4 P_4\,P4 so they align with the images of P1 P_1\,P1 and P2P_2P2. They then draw the refracted ray inside the block, GEGEGE. The student measures the angle of refraction r1 r_1\,r1 between the line GE GE\,GE and the normal as r1=23∘r_1 = 23^\circr1=23∘. (i) Calculate the ratio i1r1\displaystyle \frac{i_1}{r_1}r1i1 for this trial. Give your answer to 2 or 3 significant figures and without any unit.
The student repeats the procedure with an angle of incidence i2=50∘i_2 = 50^\circi2=50∘ and measures the new angle of refraction as r2=32∘r_2 = 32^\circr2=32∘. (i) Calculate the ratio i2r2\displaystyle \frac{i_2}{r_2}r2i2 for this trial. Give your answer to 2 or 3 significant figures and without any unit.
A classmate suggests that the ratio of the angles ir\displaystyle \frac{i}{r}ri should be a constant. State and explain briefly whether your results in (b)(i) and (c)(i) support this suggestion.
216 exam-style questions on CIE IGCSE Physics 3.2 Light, covering 3.2.1a Reflection of light, 3.2.1b Images in a plane mirror, 3.2.2 Refraction of light, 3.2.2a Refraction of light, 3.2.2b Total internal reflection, 3.2.2c Refractive index and critical angle, 3.2.2d Optical fibres, 3.2.3a Converging and diverging lenses, 3.2.3b Ray diagrams and the nature of images, 3.2.3c Virtual images and the magnifying glass, 3.2.3d Correcting long-sightedness and short-sightedness, and 3.2.4 Dispersion of light. Each one has a worked solution and a mark scheme showing where the marks go.