Optical microscope used at the Wiki Science Competition 2017 in Thailand
A ray of light being refracted in a plastic block.
18th-century microscopes from the Musée des Arts et Métiers, Paris
Refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the phase velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1; that is, the ray in the higher-index medium is closer to the normal.
Carl Zeiss binocular compound microscope, 1914
A pen partially submerged in a bowl of water appears bent due to refraction at the water surface.
Electron microscope constructed by Ernst Ruska in 1933
When a wave moves into a slower medium the wavefronts get compressed. For the wavefronts to stay connected at the boundary the wave must change direction.
Fluorescence microscope with the filter cube turret above the objective lenses, coupled with a camera.
A pencil part immersed in water looks bent due to refraction: the light waves from X change direction and so seem to originate at Y.
Types of microscopes illustrated by the principles of their beam paths
An image of the Golden Gate Bridge is refracted and bent by many differing three-dimensional drops of water.
Evolution of spatial resolution achieved with optical, transmission (TEM) and aberration-corrected electron microscopes (ACTEM).
The sun appears slightly flattened when close to the horizon due to refraction in the atmosphere.
Unstained cells viewed by typical brightfield (left) compared to phase-contrast microscopy (right).
Heat haze in the engine exhaust above a diesel locomotive.
Modern transmission electron microscope
Mirage over a hot road.
Transmission electron micrograph of a dividing cell undergoing cytokinesis
Water waves are almost parallel to the beach when they hit it because they gradually refract towards land as the water gets shallower.
Leaf surface viewed by a scanning electron microscope.
First atomic force microscope

The most common microscope (and the first to be invented) is the optical microscope, which uses lenses to refract visible light that passed through a thinly sectioned sample to produce an observable image.

- Microscope

It is what optical lenses are based on, allowing for instruments such as glasses, cameras, binoculars, microscopes, and the human eye.

- Refraction
Optical microscope used at the Wiki Science Competition 2017 in Thailand

2 related topics

Alpha

A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.

Light

Electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye.

Electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye.

A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.
The electromagnetic spectrum, with the visible portion highlighted
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Beam of sun light inside the cavity of Rocca ill'Abissu at Fondachelli-Fantina, Sicily
Due to refraction, the straw dipped in water appears bent and the ruler scale compressed when viewed from a shallow angle.
Hong Kong illuminated by colourful artificial lighting.
Pierre Gassendi.
Christiaan Huygens.
Thomas Young's sketch of a double-slit experiment showing diffraction. Young's experiments supported the theory that light consists of waves.
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This change of direction is known as refraction.

Magnifying glasses, spectacles, contact lenses, microscopes and refracting telescopes are all examples of this manipulation.

A biconvex lens

Lens

A biconvex lens
Lenses can be used to focus light
Light being refracted by a spherical glass container full of water. Roger Bacon, 13th century
Lens for LSST, a planned sky surveying telescope
Types of lenses
The position of the focus of a spherical lens depends on the radii of curvature of the two facets.
A camera lens forms a real image of a distant object.
Virtual image formation using a positive lens as a magnifying glass.
Images of black letters in a thin convex lens of focal length f are shown in red. Selected rays are shown for letters E, I and K in blue, green and orange, respectively. Note that E (at 2f) has an equal-size, real and inverted image; I (at f) has its image at infinity; and K (at f/2) has a double-size, virtual and upright image.
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An aspheric biconvex lens.
Close-up view of a flat Fresnel lens.

A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction.

Other uses are in imaging systems such as monoculars, binoculars, telescopes, microscopes, cameras and projectors.