Physics (AS & A Level) · Oct / Nov 2018 · Paper 11 · Question 29

A beam of light consists of two wavelengths of 436 nm and 654 nm. A diffraction grating of 5.00 × 10^5 lines m^–1 produces a diffraction pattern in which the second order of one of these wavelengths occurs at the same angle θ as the third order of the other wavelength. What is the angle θ?

1. A19.1°
2. B25.8°
3. C40.8°
4. D78.8°

As printed in the paper