Convex Mirror Q&A
Q: What is the mirror formula for a convex mirror?
A: The mirror formula for both concave and convex mirrors is:
1/f = 1/u + 1/v
Q: What are the sign conventions for a convex mirror?
A: For a convex mirror, we apply the following sign conventions:
- Focal length (f): Positive, because the focal point is behind the mirror.
- Object distance (u): Negative, as the object is placed in front of the mirror.
- Image distance (v): Negative, because the image is virtual and formed behind the mirror.
Q: How do I apply the mirror formula for a convex mirror?
A: Follow the same mirror formula:
1/f = 1/u + 1/v
Apply the correct signs:
- u: Negative (object is in front of the mirror).
- v: Negative (virtual image behind the mirror).
- f: Positive (for convex mirrors).
Q: Can you give an example using the convex mirror formula?
A: Sure! Let’s say you have a convex mirror with a focal length of 10 cm, and the object is placed at -20 cm:
1/10 = 1/(-20) + 1/v
Solving for v:
v = -6.67 cm
This means the image is virtual, formed 6.67 cm behind the mirror.
Q: Why is the focal length positive but the image distance negative in a convex mirror?
A: The focal length is positive because it is a virtual focus behind the mirror. According to the sign convention, the focal point is treated as positive for convex mirrors. However, the image distance is negative because virtual images, which appear behind the mirror, are always assigned negative values in the mirror sign convention.