Light Chapter Rapid Revision
Introduction
- Light is a large and important chapter.
- Challenges exist in both numerical and theory.
- Today's goal: Revision in 15-20 minutes.
- For detailed study, a one-shot video is available.
Characteristics of Light
- Light always travels straight.
- Speed: (3 \times 10^8) meters/second.
Reflection
- Definition: Light bouncing back from a shiny surface.
- Laws of Reflection:
- The incident ray, reflected ray, and normal lie in the same plane.
- Angle of incidence = Angle of reflection.
Plane Mirror
- Image is always virtual and erect.
- Size of image is equal to the object.
- Image forms behind the mirror at the same distance as the object in front.
- Image is laterally inverted.
Spherical Mirrors
- Two types of mirrors: Concave and Convex.
- Concave: Reflecting surface inward.
- Convex: Reflecting surface outward.
Mirror Concepts
- Pole: Middle point of the mirror.
- Principal Axis: Main axis passing through the pole.
- Center of Curvature (C): Center point of the mirror's curve.
- Radius of Curvature (R): Distance from C to pole.
- Focus (F): Midpoint between pole and C.
- Focal Length (f): Distance from pole to focus.
- Aperture: Total diameter of the reflecting surface.
Mirror Rules
- Parallel ray always passes through focus.
- Ray passing through focus will go parallel.
- Ray coming from the center of curvature will reflect back in the same direction.
- Rays hitting the pole have equal angles.
Ray Diagrams for Concave and Convex Mirrors
- Trick: Remember with a numbering system.
- Image location based on various positions.
Refraction
- Bending of light when it goes from one medium to another.
- Snell's Law: (\sin i/\sin r = \text{refractive index})
Refractive Index
- Measures a medium's power to bend light.
- Formula: (c/v)
Lenses
- Concave and Convex lenses.
- Concave: Diverging, Convex: Converging.
Lens Rules
- Parallel ray emerges from the focus.
- Ray coming from focus goes parallel.
- Light passing through optical center goes straight.
Lens Ray Diagrams
- Different cases for convex and concave lenses.
Formulas
- Mirror Formula: (1/v + 1/u = 1/f)
- Lens Formula: (1/v - 1/u = 1/f)
- Magnification: (-v/u) (for mirror), (v/u) (for lens)
Power of a Lens
- Power: Ability to converge or diverge.
- Unit: Diopter
- Formula: (1/f)
Homework
- Answer the given questions in comments. Display homework questions on the screen.
This revision covers the main points of the Light chapter.