Paper 4 Atomic Structure Drills

Q1 Measuring an Emission-Line Wavelength

A student uses a diffraction grating with $600$ lines per millimetre to measure the first-order diffraction angle $\theta$ of one emission line. Three readings are obtained:

reading	1	2	3
$\theta$/degrees	19.4	19.6	19.5

1. Calculate the grating spacing $d$ in metres. [2]
2. Calculate the mean angle and estimate its absolute uncertainty as half the range. [2]
3. Use $d\sin \theta =\lambda$ to determine the wavelength $\lambda$. [2]
4. Recalculate $\lambda$ at the upper and lower limits of $\theta$ and hence estimate the absolute uncertainty in $\lambda$. [3]
5. Calculate the photon energy. Use $h=6.63\times 10^{-34}\mathrm{J}\mathrm{s}$ and $c=3.00\times 10^8\mathrm{m}{\mathrm{s}}^{-1}$. [2]
6. State one improvement that would reduce the angular uncertainty and one relevant safety precaution. [2]

Q2 Rutherford Experiment Evaluation

1. State why a thin foil was used. [1]
2. State why alpha particles were suitable projectiles. [2]
3. Explain one limitation of using scattering alone to infer a full atomic model. [2]