30. In the figure given below, a narrow beam of white light is shown to pass
through a triangular glass prism. After passing through the Prism, it
produces a spectrum xy on the screen.
i.
ii.
iii.
Name the phenomenon
State the colours seen at x & y.
Why do different colours of white light bend at different angles
through a prism?
Answers
Prism
OPTICS
Prism, in optics, piece of glass or other transparent material cut with precise angles and plane faces, useful for analyzing and reflecting light. An ordinary triangular prism can separate white light into its constituent colours, called a spectrum. Each colour, or wavelength, making up the white light is bent, or refracted, a different amount; the shorter wavelengths (those toward the violet end of the spectrum) are bent the most, and the longer wavelengths (those toward the red end of the spectrum) are bent the least. Prisms of this kind are used in certain spectroscopes, instruments for analyzing light and for determining the identity and structure of materials that emit or absorb light.
refraction; prism
refraction; prism
White light entering a prism is bent, or refracted. This separates the light into its constituent wavelengths. Each wavelength of light has a different color based on the angle at which it bends. The colors of white light always emerge through a prism in the same order—red, orange, yellow, green, blue, indigo, and violet.Prisms can reverse the direction of light by internal reflection, and for this purpose they are useful in binoculars.
reflection of light
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optics: Reflecting prisms
Reflecting prisms are pieces of glass bounded by plane surfaces set at carefully specified angles. Some…
Prisms are made in many different forms and shapes, depending on the application. The Porro prism, for example, consists of two prisms arranged both to invert and to reverse an image and are used in many optical viewing instruments, such as periscopes, binoculars, and monoculars. The Nicol prism consists of two specially cut calcite prisms bonded together with an adhesive known as Canada balsam. This prism transmits waves vibrating in one direction only and thus produces a plane-polarized beam from ordinary light.
Reflecting prisms
Reflecting prisms are pieces of glass bounded by plane surfaces set at carefully specified angles. Some of these surfaces transmit light, some reflect light, while some serve both functions in succession. A prism is thus an assembly of plane reflectors at relatively fixed angles, which are traversed in succession by a beam of light.
The simplest prism is a triangular block of glass with two faces at right angles and one at an angle of 45°. The face at 45° deflects a beam of light through a right angle. The common Porro prism used in a pair of binoculars contains four 45° reflecting surfaces, two to reverse the beam direction in the vertical plane and two in the horizontal plane (Figure 7). These reflecting faces could be replaced by pieces of mirror mounted on a metal frame, but it is hard to hold mirrors rigidly and harder still to keep them clean. Some microscopes are equipped with a 45° deflection prism behind the eyepiece; this prism may provide two or three reflections depending on the type of image inversion or left-for-right reversal required.
Figure 7: Porro prism.
Prisms containing a semireflecting, semitransmitting surface are known as beam splitters and as such have many uses. An important application is found in some colour television cameras, in which the light from the lens is divided by two beam splitters in succession to form red, green, and blue images on the faces of three image tubes in the camera.