Plane Mirror
A plane mirror is a flat, highly polished reflective surface that forms a virtual, upright, and laterally inverted image of an object, with the image appearing to be the same distance behind the mirror as the object is in front of it. The image is the same size as the object (magnification = 1) and cannot be projected on a screen because it is virtual. Plane mirrors are used in everyday mirrors, periscopes, kaleidoscopes, and laser beam steering.
Properties of Images Formed by a Plane Mirror
| Property | Description | Value/Type |
|---|---|---|
| Image nature | Cannot be projected on screen | Virtual |
| Image orientation | Same up/down as object | Upright |
| Lateral inversion | Left–right swapped | Laterally inverted |
| Image distance | Equal to object distance | d_image = d_object |
| Magnification | Same size as object | m = +1 |
| Image location | Behind the mirror surface | Same depth as object distance |
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Related Terms
Light Reflection
Light reflection is the phenomenon in which a light ray bounces off a surface and changes direction, obeying the law of reflection: the angle of incidence equals the angle of reflection, both measured from the normal to the surface. It is fundamental to how we see non-luminous objects, as surfaces reflect light into our eyes. Applications range from mirrors in optical instruments to reflective coatings on road signs and safety gear.
Convex Lens
A convex lens (also called a converging lens) is an optical element that is thicker at its centre than at its edges, causing parallel rays of light passing through it to converge toward a single real focal point on the far side. The converging power arises from refraction at both curved surfaces, and the focal length is positive. Convex lenses are used in magnifying glasses, cameras, projectors, the human eye's cornea and crystalline lens, and corrective spectacles for hyperopia (long-sightedness).
Optical Dispersion
Optical dispersion is the phenomenon in which the refractive index of a medium varies with the wavelength (frequency) of light, causing different colours to refract by different amounts and thereby separate from one another when passing through a dispersive medium such as a glass prism or water droplet. Shorter wavelengths (violet) are refracted more than longer wavelengths (red) in normal dispersion. Dispersion is responsible for the formation of rainbows, chromatic aberration in lenses, and the spectral analysis of light sources.
From Latin "planus" meaning "flat" or "level". The word "mirror" derives from Old French "mireor" and Latin "mirare" (to look at). Polished metal mirrors were used in ancient Egypt as far back as 3000 BCE; silvered glass mirrors were first produced in Venice in the 13th century CE.