A) Why a concave mirror is better than a plane mirror as a shaving mirror.

Here's an explanation regarding concave mirrors for shaving:

a) Why a concave mirror is better than a plane mirror as a shaving mirror.
A concave mirror is preferred over a plane mirror for shaving because when an object (like a face) is placed between the pole and the principal focus of a concave mirror, it forms a magnified, upright, and virtual image. This allows for a larger, clearer view of the face, making shaving easier and more precise. A plane mirror always produces an image of the same size as the object.

b) Why is the image not to be seen in the concave mirror and suggest how to get the required image.
If the image is not seen in the concave mirror, it means the object (face) is likely placed beyond the principal focus or at the principal focus. In these cases, the image formed is either real, inverted, and diminished/magnified (beyond focus) or formed at infinity (at focus), making it difficult or impossible to see clearly. To get the required magnified, upright image for shaving, the object must be placed between the pole and the principal focus of the concave mirror. The person needs to adjust their distance from the mirror until their face is within this specific range.