11/7/2023 0 Comments Laser diffraction grating lab![]() The various orders of diffracted images of the laser beam can be directly visualized on the screen. Place the grating normal to the laser beam. Λ = Wavelength of laser light (6700*10 -8cm) Students will be able to study diffraction patter using mono and polychromatic sources (create)Īim: To find the wavelength of the laser light using diffraction grating.Īpparatus: Diode laser, Diffraction grating, Screen, Scale and thin rope. Students will be able to calculate the wavelength of given source (evaluate) Learning Objectives for in class and out of classĭefine LASER, Diffraction and grating in laser diffraction experiment (Recall level)ĭescribe how diffraction patter occurs using LASER light (Understand level)Ĭompare the diffraction patter using different gratings such as 15000 lines/inch, 7500 lines/inch and 2500 lines/inch. Then calculate the wavelength of each colour.ĭetermination of wavelength for prominent lines.Note the readings on the verniers and calculate the diffraction angle. ![]() ![]() Telescope is moved to make the cross-wire coincide with each line of the spectrum.To calculate the wavelegth of different lines Then from the equation, number of lines per unit length of the grating can be calculated. Calculate the difference in the reading to obtain the diffraction angle.Turn the telescope to both sides to obtain green lines.Note the reading of both the verniers.Turn the telescope to obtain the image of the slit.Calibrating Telescope Button : Helps the user to calibrate the telescope after starting the experiment, if needed.Telescope Angle Slider : Helps make minute changes of the telescope angle.Vernier Angle Slider : This slider helps the user to change the angle of the Vernier.Telescope Angle Slider : This slider helps the user to change the angle of telescope.Grating Toggle Button : Helps the user to place or remove the grating.Light Toggle Button : Helps the user to switch the lamp ON or OFF.The Start Button can be activated only if the focus of the telescope is proper. Start Button : Helps the user to start the experiment after setting the focus of telescope.Telescope Calibrate Slider : This slider helps the user to change the focus of telescope.Spectrometer, Grating and Mercury Vapour Lamp. The user can use a grating spectrometer to measure the wavelengths of Yellow, Green, Violet and Red lines in the visible spectrum of Mercury. The simulation virtualizes the Mercury spectrum experiment. Using this value of N, the wavelengths of the other prominent lines in this spectrum are calculated. The number of lines per meter (N) of the grating is calculated. The wavelength of the green line is 546.1 x10 -9m. Thus the angle of diffraction θ for each spectral line is determined. The mean value of this difference gives 2θ-twice the angle of diffraction. ![]() The difference between the readings on the left and right on the same vernier is determined for each line. The telescope is then moved to the right and the reading of different lines is similarly taken. The vertical cross wire is then made to coincide with the other lines on the left and the vernier readings are taken in each case. On the either side of the direct image, the diffraction spectra are seen.The telescope is turned slowly towards the left so that the vertical cross wire coincides with the violet lines of the first order. The telescope is then released and is brought to observe the direct image. The vernier table is firmly clamped in this position. The vernier table is then released and rotated exactly through 45° in the proper direction so that the surface of the grating becomes normal to the incident light. The prism table is fixed and after making fine adjustments with the tangential screw, the readings of the vernier are noted. The leveling screws are adjusted so that the image is at the centre of the field of view of the telescope. The vernier table is released and is slowly rotated till the reflected image coincides with the vertical cross wire. The grating is mounted vertically on the prism table with its ruled surface facing the collimator. Now, the telescope is rotated exactly through 90° and is fixed in this position. The telescope is brought in a line with the collimator and the direct image of the slit is made to coincide with the vertical cross wire. The slit is illuminated by mercury vapour vamp. The preliminary adjustments of the spectrometer are made.
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