Which point on the wave diagram below are 90° out of phase with each other?

4.  D and E

Explanation:

As we know that the relation between phase difference and path difference is given below

now we have to find the distance of two points which are out of phase by 90 degree

so here we will have

so from above we have

so the distance between the points will be 1/4 times of wavelength

so here correct answer is

4. D and E

c.the charges if the proton and electron and gravity

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