Answer:
Principal focus of a concave mirror. The principal focus of a concave mirror is a point on its principal axis to which all the light rays are parallel and close to the axis converge after reflection from the concave mirror.
Focal length of a concave mirror. The focal length of a concave mirror is the distance between its pole and the principal focus
The reflecting surface of a spherical mirror forms a part of a sphere. The centre of this sphere. This point is called the centre of curvature of the spherical mirror. Center of curvature can also be defined as the point in the centre of the sphere from which the mirror was sliced. It is represented by the letter C. Please note that the centre of curvature lies outside the mirror's reflecting surface. The centre of curvature of a concave mirror lies in front of it. However, it lies behind the mirror in case of a convex mirror.
If a concave mirror were thought of as being a slice of a sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror. This line is known as the principal axis.
Answer:
a) counterclockwise
Explanation:
The Lenz's Law establish that the direction of the induced current is in an opposite direction, in comparison with the change od the magnetic flux.

Specifically, if the flux decreases the induced current is in a counterclockwise direction, if increases, the direction is in a clockwise direction.
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Answer:
Many things, such as building the Great Wall of China, and building highways.
Explanation:
They would feel warmer cause black attracts heat and also could attract bees
I think the correct answer would be the child quietly sits until the timer goes off. It is ineffective because the child would be used to this process and would come to a time where he will not get something from it.Also, it would make a child feel isolated and alone which would affect hi self-esteem in a long run.