9. Light – Reflection and Refraction
This chapter discusses the fundamental properties of light, focusing on the phenomena of reflection and refraction. It explains how light behaves with mirrors, including spherical mirrors and their applications, as well as the properties and behavior of lenses. The chapter covers key concepts such as the laws of reflection, image formation by mirrors and lenses, and the derivation of mirror and lens formulas, concluding with the concept of power in lenses.
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What we have learnt
- Light travels in straight lines within a transparent medium.
- Mirrors and lenses can form real or virtual images, depending on the object's position.
- The New Cartesian Sign Convention is crucial for determining distances in mirror and lens equations.
- The lens formula and mirror formula relate object distance, image distance, and focal length.
- The power of a lens is the reciprocal of its focal length and is measured in dioptres.
Key Concepts
- -- Laws of Reflection
- The laws indicating that the angle of incidence is equal to the angle of reflection, and both rays with the normal and the incident ray lie in the same plane.
- -- Concave and Convex Mirrors
- A concave mirror curves inward and can produce real images, while a convex mirror curves outward, producing virtual images.
- -- Focal Length
- The distance from the mirror or lens at which parallel rays converge or appear to diverge, dependent on the curvature.
- -- Refractive Index
- The measure of how much the speed of light is reduced in a medium compared to its speed in vacuum.
- -- Magnification
- The ratio of the height of the image to the height of the object, indicating how much larger or smaller the image is compared to the object.
- -- Power of a Lens
- The ability of a lens to converge or diverge light, defined as the reciprocal of the focal length, indicated in dioptres.
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