Final answer:
The angle of 60 degrees will produce the highest image contrast in a diffraction grating because larger angles lead to greater separation of the diffraction maxima, allowing for clearer distinction between colors in the spectrum.
Step-by-step explanation:
The question is related to diffraction grating and image contrast, which corresponds to how dispersed the light is and how distinguishable the light and dark areas are in the patterns observed. Image contrast is impacted by the diffraction angle, with larger angles generally producing higher contrast due to greater separation of the maxima. Referring to the provided information, particularly the one mentioning a diffraction grating producing first-order maxima at a certain angle, and knowing that the longest wavelength of visible light will diffract more (larger angle) compared to the shortest, we can infer that larger angles will yield higher contrast.
Given the choice of angles, the angle of 60 degrees will produce the highest image contrast because it signifies a greater separation between diffraction orders, ensuring that each color in the spectrum is more clearly separated from the others. Therefore, the answer to the student’s question is 4. 60.