7. A concave mirror forms on a screen an image of twice the linear dimensions of the object Objcct and screen are then moved until the image is three times the size of
the object. If the shift of the screen is 20cm, determine the shifts of the object and
the focal length of the mirror.

The earth's magnetic field, with a magnetic dipole moment of 8.0×1022am2, is generated by currents within the molten iron of the earth's outer core. suppose we model the core current as a 3000-km-diameter current loop made from a 1000-km-diameter “wire.” the loop diameter is measured from the centers of this very fat wire.to decide whether this is a large or a small current density, compare it to the current density of a 7.0 a current in a 2.0-mm-diameter wire.