A Level Physics Practice Exam

What happens to subsidiary maxima when the light source is changed to white light?

1. They disappear

2. They retain their original color

3. They form a continuous spectrum

4. They only produce red spectra

The correct answer is: They form a continuous spectrum

When the light source is changed to white light, subsidiary maxima will form a continuous spectrum. This occurs because white light is made up of multiple wavelengths corresponding to different colors, from red to violet. Each wavelength will diffract and interfere to produce maxima and minima at different locations on the observation screen. As a result of this wavelength dependency, instead of seeing distinct lines of color at the maxima, the overlapping of these maxima from various wavelengths creates a spectrum. The different colors blend into one another due to the gradual change in the angle of diffraction for various wavelengths of light. Thus, instead of discrete colors associated with a monochromatic light source, white light facilitates the formation of a continuous band of colors – a spectrum. In summary, using white light leads to the emergence of a continuous spectrum at the subsidiary maxima due to the combination of all the colors present in white light interfering constructively at various points, rather than maintaining discrete colors.