Question

Diffraction grating #1 has half the lines/cm that diffraction grating #2 does. When used with a certain wavelength of light, both gratings give first order maxima. Which of the following statements is true for the same wavelength of light.

Answer 1

Grating #2 must give a second order maximum.

Both gratings must also give second order maxima.

It is possible that neither grating gives a second order maximum.

Grating #1 must give a second order maximum.

Answer 2

Grating #1, which has less dispersion, will have a second order maximum where grating # 2 has its first order maximum.

Choose the last answer.