A Ball Swinging in Front of a Concave Mirror, Highlighting the Inversion of an Image when an Object Passes the Mirror’s Focal Point. (More Info in the Comments)


A Ball Swinging in Front of a Concave Mirror, Highlighting the Inversion of an Image when an Object Passes the Mirror’s Focal Point. (More Info in the Comments)

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  1. (Video Via Physics Demos on YouTube)
    Concave mirrors like these are generally used in certain medical and industrial apparatus. For example, Ophthalmoscopes utilise a Concave mirror to allow a doctor to view a patient’s retina, and Solar Furnaces focus heat. Concave mirrors are often used in vehicle headlights as well, with the light source at the focus point of the mirror to create light that can travel parallel for long distances. ⠀

    At the Focal Point (the place where the ball naturally hangs when not swinging), the light rays reflected from the mirror never actually meet and cannot create a focused image. For this reason, the image at the focal point Is extremely large and indistinct. ⠀

    When the ball is close to the mirror (past the Focal Point) the image is practically identical, but as it moves away, the image of the ball appears larger (because the image focuses “further away” and therefore gets “stretched”) and is what is known as a Virtual Image.⠀

    Past the Focal Point, the ball suddenly becomes inverted. This is because the light rays hit the concave mirror and cross over each other at the focal point, presenting an upside-down image.

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