Ray Diagrams for Concave Mirrors
Key Concepts
- Principal Axis: Horizontal line through the mirror's center.
- Center of Curvature (C): Center of the circle from which the mirror is a part.
- Focal Point (f): Point halfway between mirror and C, distance is called focal length.
- Focal Length: Distance from the mirror to focal point (f is 1/2 of C).
Ray Diagram Rules
- Ray diagrams for concave mirrors follow similar rules to convex lenses.
- Parallel-f Rule:
- First ray goes parallel to the principal axis, reflects through f.
- f-Parallel Rule:
- Second ray goes through f, reflects parallel to the principal axis.
Image Characteristics by Object Position
Object Beyond C
- Image Position: Between C and f.
- Image Size: Smaller than object.
- Image Orientation: Inverted.
- Image Type: Real image (light rays converge).
Object at C
- Image Position: At C.
- Image Size: Same size as object.
- Image Orientation: Inverted.
- Image Type: Real image.
Object Between C and f
- Image Position: Beyond C.
- Image Size: Larger than object.
- Image Orientation: Inverted.
- Image Type: Real image.
Object at f
- Image: No image formed; rays are parallel and do not converge.
Object Inside f
- Image Position: Behind the mirror.
- Image Size: Larger than object.
- Image Orientation: Erect (upright).
- Image Type: Virtual image (rays diverge).
Patterns and Comparisons
- Converging Devices: Concave mirrors and convex lenses have similar image characteristics.
- Pattern: As the object approaches the mirror/lens, the image moves further and gets larger, changing from inverted to erect inside the focal point.
Summary Table
- Concave Mirror:
- Object greater than C: Image between C and f, inverted, real.
- Object at C: Image at C, same size, inverted, real.
- Object between C and f: Image beyond C, magnified, inverted, real.
- Object at f: No image.
- Object inside f: Image behind mirror, magnified, erect, virtual.
Study Tips
- Focus on learning the rules and patterns, not memorizing each case.
- Practice drawing ray diagrams using straight edge and sharp pencil.
Conclusion
- Understanding these concepts helps in predicting image characteristics without memorizing.
Thank you for watching! Further exploration in lenses and mirrors will continue in the next video.