A student is investigating the refraction of light through a rectangular transparent block with parallel opposite sides on a ray-trace sheet. They trace an incident ray striking the block at an angle of incidence i=40∘i = 40^\circi=40∘. The measured angle of refraction inside the block is r1=25∘r_1 = 25^\circr1=25∘.
State the expected angle of emergence, with respect to the normal, when the light ray exits the opposite parallel face of the block into the air.
State the minimum recommended separation distance between the locating tracking pins (e.g., P3 P_3\,P3 and P4P_4P4) used to trace the emergent ray to ensure high accuracy.
Describe two practical precautions that should be taken when placing or viewing the pins in this experiment to obtain reliable results.
The student rotates the block by 90∘ 90^\circ\,90∘ and repeats the measurement under the same conditions, obtaining an angle of refraction of r2=27∘r_2 = 27^\circr2=27∘. State whether these two measurements support the claim that the angle of refraction is the same in both orientations. Justify your answer with reference to experimental limits.
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.