A student investigates the reflection of light by a plane mirror to analyze the relationship between the angle of incidence θ\thetaθ and a ratio of measured lengths, r=abr = \frac{a}{b}r=ba.
The student's results are recorded in the table below:
θ/∘a/cmb/cmr=ab122.110.2...................244.410.90.40367.312.40.59\begin{array}{|c|c|c|c|} \hline \theta / ^\circ & a / \text{cm} & b / \text{cm} & r = \frac{a}{b} \\ \hline 12 & 2.1 & 10.2 & \text{...................} \\ \hline 24 & 4.4 & 10.9 & 0.40 \\ \hline 36 & 7.3 & 12.4 & 0.59 \\ \hline \end{array}θ/∘122436a/cm2.14.47.3b/cm10.210.912.4r=ba...................0.400.59
Calculate the ratio r=abr = \frac{a}{b}r=ba for θ=12∘\theta = 12^\circθ=12∘. Record your answer to 2 significant figures in the table.
The student states that the ratio rrr is directly proportional to the angle of incidence θ\thetaθ.
State whether you agree or disagree with the student's statement. Justify your answer using values from the table.
Suggest how the student can modify their procedure to obtain more reliable data and increase confidence in their conclusion.
Suggest one major source of inaccuracy in this reflection experiment, even if it is carried out very carefully.
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.