Monday, April 10, 2017

A student attempts to show the interference of light using two identical green LEDs.




Question 1
A student attempts to show the interference of light using two identical green LEDs.
Which statement explains why the experiment will not succeed?
A The light waves from the sources are not coherent.
B The light waves from the sources do not have the same amplitude.
C The light waves from the sources have a range of wavelengths.
D The light waves from the sources are not monochromatic.





Reference: Past Exam Paper – June 2014 Paper 13 Q28





Solution 1:
Answer: A.
Interference occurs when the light waves are coherent (that is, they have constant phase difference and the same frequency). So, if they light waves from the sources are not coherent, the experiment will not succeed.

Amplitude is not a condition for interference.

Since the LEDs are identical, they are monochromatic and have the same wavelength.

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