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Light Energy

How light bends as it passes between media, how white light splits into colours, and how concave and convex mirrors form images.

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What this chapter covers

  1. Refraction of Light

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    • Speed of Light in Different MediaFastest in air, slower when denser.
    • Definition and TermsLight changes direction between transparent media.
    • Laws of RefractionSame plane; sin i/sin r constant.
    • Refraction Through a Rectangular Glass BlockEmergent ray parallel to incident ray.

  2. Effects of Refraction

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    • Apparent DepthObjects in water appear shallower.
    • Early Sunrise and Late SunsetSun's rays bend through atmospheric layers.
    • Mirage in a DesertHot air makes illusory water pools.

  3. Dispersion of White Light

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    • PrismBends light towards its base.
    • SpectrumWhite light splits into seven colours.
    • Cause of DispersionViolet bends most, red bends least.

  4. Spherical Mirrors

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    • Formation and TypesSilvered part of a hollow sphere.
    • Terms Related to Spherical MirrorsPole, centre of curvature, principal axis.
    • Focus and Focal LengthWhere parallel rays converge or diverge.
    • Ray Diagram RulesObey laws of reflection; i = r.
    • Real and Virtual ImagesReal caught on screen; virtual cannot.
    • Images by a Concave MirrorDepends on where the object is.
    • Images by a Convex MirrorAlways virtual, erect and diminished.
    • Uses of Concave MirrorShaving mirrors, torches, searchlights, headlights.
    • Uses of Convex MirrorRear-view mirrors and street-lamp reflectors.

Try a sample question

A coin lying at the bottom of a vessel filled with water appears to be:

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