Answer: (C) Slide against each other
Explanation:
Think about rubbing our palms together, and they get warm that right there is friction.
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*Explanation:* maybe add another?
Electricity is just the flow of electrons or charges from a point of production through a conductor, to another point where it can be utilized or converted to another form of energy.
Magnetism is the force exerted by magnets when they attract or repel each other. Magnetism is caused by the motion of electric charges from two or more magnetic substances.
To solve this problem it is necessary to apply the concepts related to destructive interference.
The concept refers to an overlap of two or more waves of identical or similar frequency that, when interfering, creates a new pattern of waves of lower intensity
By definition destructive interference is given by

Where,

n=integer (1,2,3,4,5,6...etc)
t = thickness
M= Index of refrqaction
For minimum thickness to satisfy this condition n will be minimum there,
n=0
Therefore

Solving to find M,



Therefore the correct answer is B. 1.38