The radiation is ultra voilet or Gamma radiation , because their wave length is very short i e 1..0 to 2.5 (angstrom)Ao.
Answer:
The angle between the electric field lines and the equipotential surface is 90 degree.
Explanation:
The equipotential surfaces are the surface on which the electric potential is same. The work done in moving a charge from one point to another on an equipotential surface is always zero.
The electric field lines are always perpendicular to the equipotential surface.
As

For equipotential surface, dV = 0 so

The dot product of two non zero vectors is zero, if they are perpendicular to each other.
M=2.45 because you multiply out the equation on the right and divide by 10