The slit is made very narrow.Īdjustment of prism table - The prism table is leveled using the spirit level or by optical method. The image of the slit is observed through the telescope and is made to coincide with the vertical cross wire. The telescope is brought in line with a collimator. The telescope is attached to a circular scale and can be rotated about a vertical axis through the centre of the scale.Ĭheck spectrometer, prism experiments of optical lab Īdjustment of telescope - The telescope is adjusted by looking to a distant object, until the object cross wires are in sharp focus.Īdjustment of the collimator - The slit is opened slightly and is illuminated using the sodium lamp. Cross hairs located in the focal plane of the objective lens. Telescope: An objective lens that focuses on the entering parallel rays in a plane so that the real image can be observed with the aid of the eyepiece. The Vernier table and hence verniers can be fixed in any position by means of radial screw. Two verniers are attached to the Vernier table and they move along the circular scale, when the Vernier table is rotated. Vernier table: The Vernier table is also circular in shape and can be rotated about a vertical axis. A central horizontal shelf for mounting either a prism or a grating. Prism table: The prism table is circular in shape and is provided with three leveling screws. It consists of an adjustable slit and convex lens. Direction of all rays should be same and for this light which is to be analyzed must pass through the grating as parallel beam.Ĭollimator: The collimator is used to produce parallel rays. Spectrometer is an instrument which is used to measure the intensity and other properties of light. Where, m is called the order of the spectrum, λ the wavelength, N the number of lines per cm and θ the diffraction angle measured with respect to the direction of the light incident on the grating. In general the grating equation for constructive maxima is, Complete constructive interference occurs when the phase or path difference is equal to some whole number of the wavelength. The slits of a grating give rise to diffraction and the diffracted light interferes so as to set up interference patterns. The ruled widths are opaque to light and space between any two successive lines is transparent and act as parallel slits.Number of rulings per cm of grating used in visible region varies from 5,000 to 12,000 lines per mm. It consists of a very large number of equidistant narrow parallel rectangular slit of equal width separated by equal opaque portion. The diffraction grating provides the simplest and most accurate method for measuring wavelengths of light. In this experiment a diffraction grating optical spectrometer is used to study the spectra. Emission spectra-bright lines on dark background.Absorption spectra-dark lines on a bright background.Continuous spectra-continuous band of colors is obtained.There are several types of spectra mainly, These radiations are seen in the form of spectra. When an atom or ion in substance got excited, they emit radiations of particular frequencies. Spectrometer, diffraction grating, mercury bulb, Hydrogen Bulb, neon bulb, etc. To study the emission spectra of Hydrogen, Neon and mercury vapours.
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