Question 15
Two wave sources are
oscillating in phase. Each source produces a wave of wavelength λ.
The two waves from the sources meet at point X with a phase difference of 90°.
What is a possible
difference in the distances from the two wave sources to point X?
A λ / 8 B λ / 4 C λ / 2 D λ
Reference: Past Exam Paper – June 2017 Paper 12 Q29
Solution:
Answer: B.
The 2 sources are in
phase.
A distance equal to the
wavelength corresponds to a phase difference of 360° (that is they are in phase – or phase
difference = 0°).
360° - - - > λ
1° - - - > λ / 360
90° - - - > (λ / 360) ×
90 = λ / 4
So, a phase difference of 90° corresponds to a distance equal to λ / 4.
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