Light: Reflection and Refraction

• Light and Vision: Light is a form of energy that makes things visible. We see objects because they reflect light into our eyes.

• Reflection of Light: When light bounces off a surface, it's called reflection. Mirrors are highly reflective surfaces.

  • Laws of Reflection:

    • The angle of incidence (incoming light) equals the angle of reflection (outgoing light).

    • The incident ray, reflected ray, and the normal (a line perpendicular to the surface) all lie in the same plane.

  • Types of Mirrors:

    • Concave Mirrors: Curve inward, can create real or virtual images depending on object position. Used in telescopes, headlights, and makeup mirrors.

    • Image formation:

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      Convex Mirrors: Curve outward, always create virtual, upright, and smaller images. Used for security mirrors, car side mirrors for a wider field of view.

    • Image formation:

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• Refraction of Light: The bending of light as it passes from one medium (like air) to another (like water) is called refraction. This happens because light changes speed in different media.

  • Laws of Refraction (Snell's Law):

    • Similar to reflection, the incident ray, refracted ray, and normal all lie in the same plane.

    • The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant for a given pair of media.  

  • Refractive Index: A measure of how much a substance can bend light. Higher refractive index means light slows down more and bends more.

• Lenses: Lenses are curved pieces of glass or plastic that refract light to form images.

  • Types of Lenses:

    • Convex Lenses: Thicker in the middle, converge (bring together) light rays. Used in magnifying glasses, cameras, and eyeglasses for farsightedness.

    • Image formation:

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      Concave Lenses: Thicker at the edges, diverge (spread out) light rays. Used in eyeglasses for nearsightedness and some telescopes.

    • Image formation:F

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  • Lenses form images based on the object's position and the lens's shape. Images can be real or virtual, upright or inverted, magnified or diminished.

• Power of a Lens: Measured in diopters, it indicates how strongly a lens converges or diverges light. It's the reciprocal of the focal length (the distance between the lens and where it focuses parallel rays).

• FORMULAS:

Mirrors:

• Mirror Formula: (Very similar to the lens formula)

  • 1/f = 1/v + 1/u

  • Where:

    • f = Focal length of the mirror

    • v = Distance of the image from the mirror

    • u = Distance of the object from the mirror

• Magnification (m):  

  • m = hᵢ/h₀ = -v/u

  • Where:

    • m = Magnification

    • hᵢ = Height of the image

    • h₀ = Height of the object

  • Lenses:

    • Lens Formula (Thin Lens Equation):

      • 1/f = 1/v + 1/u

      • Where:

        • f = Focal length of the lens

        • v = Distance of the image from the lens

        • u = Distance of the object from the lens

    • Magnification (m):

      • m = hᵢ/h₀ = -v/u

      • Where:

        • m = Magnification

        • hᵢ = Height of the image

        • h₀ = Height of the object

    • Power of a Lens (P):

      • P = 1/f (in diopters)

      • Where:

        • f = Focal length of the lens (in meters)