[Physics SPM] Exam Pointers III

Source: Maths & Science Guide

Revision

1. Compare the separating distance between consecutive bright fringes of red light with that of blue light of the interference pattern obtained from a Young's double slit experiment.
   
   
2. State one observation of the interference pattern of red light in a Young's double slit experiment.

Frequent Mistakes

Student's answer:

1. The interference of red light has a bigger number of fringes due to the smaller separating distance compared to that of blue light. This is because the wavelength of red light is bigger than that of blue light.
   
   
2. Bright and dark fringes are observed due to the interference of coherent waves.

Correct Answer

1. The separating distance between consecutive bright fringes of red light is bigger than that of blue light.
   
   
2. Alternate bright and dark fringes are formed. The central fringe is the bright fringe. All the fringe sizes are equal, or the separating distance of consecutive fringes is the same.