A diffraction grating with $1000$ lines per mm is used in a spectrometer to measure the wavelengths of light emitted from a gas discharge tube. You measure the diffraction angle to be at $20$ for one emission line. What would happen to this emission line$$s diffraction angle if you replaced the diffraction grating with one having $500$ lines per mm instead?$$

Answer

The diffraction angle would be $10.$

The diffraction angle would be less than $20.$

The diffraction angle would remain at $20.$

The diffraction angle would greater than $20.$