Why are the shaving mirror concave while the rear view mirror convex? Draw
the ray diagrams to support your answer.
The reason why a shaving mirror is typically concave while a rear view mirror is convex can be understood by considering the way light rays reflect off different types of mirrors.
1. Shaving Mirror (Concave):
A concave mirror is curved inward, resembling the shape of the inner surface of a sphere. This mirror is commonly used for personal grooming, such as shaving or applying makeup. The curvature of a concave mirror causes the parallel light rays that enter the mirror to converge at a specific point called the focal point.
- To draw a ray diagram for a concave mirror:
Step 1: Draw a horizontal line to represent the principal axis of the mirror.
Step 2: Place an arrow on the left side of the line to represent the object (e.g., your face).
Step 3: Draw a line from the top of the object parallel to the principal axis and another line from the top of the object towards the center of curvature of the mirror (which is twice the focal length away).
Step 4: Where these two lines intersect on the principal axis is where the virtual image of the object will be formed.
The concave shape of the shaving mirror allows it to reflect light in such a way that it produces a magnified and upright virtual image, which is convenient for close-up personal grooming.
2. Rear View Mirror (Convex):
A convex mirror has a curved outward surface, like the shape of the outer surface of a sphere. Convex mirrors are commonly used as rear-view mirrors in vehicles as they offer a wider field of view.
- To draw a ray diagram for a convex mirror:
Step 1: Draw a horizontal line to represent the principal axis of the mirror.
Step 2: Place an arrow on the left side of the line to represent the object (e.g., a car behind you).
Step 3: Draw a line from the top of the object towards the center of curvature of the mirror (which is located behind the mirror).
Step 4: The reflected ray that returns to your eye shows the direction of the virtual image formed by the convex mirror.
The convex shape of the rear-view mirror causes light rays to diverge as they reflect off its surface. This divergence allows for a wider range of incoming rays to be reflected, resulting in a wider viewing angle. However, it also leads to the virtual image being smaller and appear closer than it actually is.
In summary, the different shapes of shaving mirrors (concave) and rear-view mirrors (convex) are designed to provide specific benefits. The concave shape of a shaving mirror allows for a magnified and upright image for detailed grooming, while the convex shape of a rear-view mirror offers a wider field of view for improved road visibility.