The image of a distant tree is virtual and very small when viewed in a curved mirror. the image appears to be 22.9 cm behind the mirror. what kind of mirror is it?
what is its radius of curvature? (in cm)

45.8 cm

Explanation:

distance of object from the mirror is infinity

distance of image, v = 22.9 cm

The mirror is convex because it is used to see the distant objects and the image formed by the mirror is erect and small.

use mirror formula

Let f be the focal length of the mirror

1 / f = 1 / v + 1 / u

1 / f = 1 / 22.9  + 1 / ∞

f = 22.9 cm

radius of curvature = 2 x focal length

radius of curvature = 2 x 22.9 = 45.8 cm

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

the answer is ampere

the ampere is used to measure electricity. an ampere is a unit of electric current equal. a unit of measure for the flow of current in a circuit. one ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance.