IIT JEE , AIEEE Forum - Physics , Modern Physics - Question-1- When we give a jerk(force) to a string ,there arise waves in the string ,so w

Saikat

Question-1- When we give a jerk(force) to a string ,there arise waves in the string ,so we can conclude that a force is
necessary for a wave .But according de-Broglie every object posses a wavelength given by - h/mv,here it is not
mentioned that any force is acting on it because the formula only states that the necessary condition to have
wavemotion is that particle must have mass and velocity(v,m not= 0).Is there any force which is responsible for
the object to move in (de-Broglie) wavemotion? If not then why if we throw a ball straight then it it will also
have a wavemotion,there must some fictitious force?
So my question is when a body is thrown in straight line it will move in wavemotion without presence of any force?
Is this wavemotion is only on earth or it is also present in zero gravity and near black holes?
Is this force acts on a body moving with a velocity comparable to that of light?

Question-2- Gravitational and electrostatic forces are centric forces(act between line joing the centre of two bodies),
but why the magnetic forces act perpendicular to the magnetic field and the velocity(plz give explanation at the
atomic level).I want to know that why the direction of that force obey the cross product rule,why force is not along
the velocity of that body or along the direction of magnetic field or in any other direction?Is this an experimental
law,because i didn't find its explanation in any textbook.

I am a student of class XII.

feynmann

q2

see in original maxwell's work there was no partial derivatives of time , only total derivative d/dt was present .

Now d/dt =

/

t + v .del

In that way a term' v X ' arises

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