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<span>Answer: </span>A swell
A wave which creates a strong undertow is called a swell. These types of waves are also known as <span>surface gravity waves.
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Answer:
σ =4.180×10^{-9} C/m^2
Explanation:
electric field due to non conducting sheet is

the force acting on the piece of Styrofoam
Eq= mg
⇒E= mg/q
now,

⇒

charge per unit area (in C/m2) on the plastic sheet σ =4.180×10^{-9} C/m^2
Take a purely random sample or to deliberately pick individuals who represents the various groups
Frequency= velocity of light/wave length
Fr= 3×10^8/510×10^-9
Frequwency=5.88×10^14 Hz