F is the focal length of the lens. A positive f indicates a converging optical device, like a convex lens or a concave mirror.
Choice A
Magnetic flux can be calculated by the product of the magnetic field and the area that is perpendicular to the field that it penetrates. It has units of Weber or Tesla-m^2. For the first question, when there is no current in the coil, the flux would be:
ΦB = BA
A = πr^2
A = π(.1 m)^2
A = π/100 m^2
ΦB = 2.60x10^-3 T (π/100 m^2 ) ΦB = 8.17x10^-5 T-m^2 or Wb (This is only for one loop of the coil)
The inductance on the coil given the current flows in a certain direction can be calculated by the product of the total number of turns in the coil and the flux of one loop over the current passing through. We do as follows:
L = N (ΦB ) / I
L = 30 (8.17x10^-5 T-m^2) / 3.80 = 6.44x10^-4 mH
<span>The answer is cleavage
Cleavage is the way minerals will break along a plane of weakness in a crystal lattice. These plane of relative weakness is formed due to various reasons like the locations of atoms in a crystal lattice so these locations form the smooth repeting surface which could be found out by studying its lattice or are sometimes visible to naked eye.</span>