3grooves ab, ac and ad are made in a circular disk lying in a vertical plane 3 particles b, c and d constrained to move along path ab, ac and ad respectively are released from point a. particle b reaches point b in time tb, particle c reaches point c in time tc and particle d reaches at point d in time td. then which of the following statements is incorrect

Ans. The correct answer is: option (a) i.e. (a)  tB = tC = tD

Since when we calculate the relative velocity of a particle with respect to another particle along the same line, then the particles can never have an equal velocity and therefore the time taken by the particles will be different and not same. Therefore, all the particles will reach at different time interval. So statement (a) is incorrect.

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

i would say