In a diffraction-grating experiment with

PHYSICS · Multi-part · A Level · Physics · Waves · Waves

Problem

500\,\text{lines/mm}

, violet light of wavelength

420\,\text{nm}

produces a third-order maximum. (1) Part 1: Determine

\theta_{\text{exact}}

for this maximum. (2) Part 2: Estimate

\theta_{\text{approx}}

by replacing

\sin\theta

with

\theta

in radians. (3) Part 3: Calculate the percentage error and state whether the approximation is acceptable if the experiment tolerates up to

1.5\%

error.