A student investigates the refraction of light through a semicircular glass block. The straight boundary of the block is aligned with a line ABABAB, and CCC is the midpoint of ABABAB. A normal line NLNLNL is drawn perpendicular to ABABAB through CCC.
State the minimum recommended distance that the student should space the locator pins along a ray line, and give one other precaution they should take to ensure the ray trace is as accurate as possible.
In one configuration, the student traces an emerging ray GCGCGC and measures the acute angle α\alphaα between this ray and the flat face boundary ABABAB to be 71∘71^\circ71∘. Calculate the angle β\betaβ between the ray GCGCGC and the normal NLNLNL.
A classmate suggests that this angle β\betaβ should theoretically be 20∘20^\circ20∘. State whether the student's experimental result supports this classmate's suggestion, and justify your answer, referring to experimental accuracy.
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.