Answer:
The focal length of a spherical mirror with a radius of curvature of +20cm is +10cm.
Step-by-step explanation:
The focal length of a spherical mirror is half of its radius of curvature. In this case, since the radius of curvature is +20cm, the focal length would be +10cm.
To determine whether the mirror forms a real or virtual image, we need to consider the sign convention. For a concave mirror (which is the case here since the radius of curvature is positive), if the object is placed beyond the focal point, a real and inverted image is formed. If the object is placed between the focal point and the mirror, a virtual and upright image is formed.
Since the question does not provide the position of the object, it is not possible to determine whether the mirror forms a real or virtual image. Additional information about the object's position relative to the focal point or mirror is required to make that determination.