Laser Grating Experiment PDF

Determination of the number lines of a given grating using a laser source for display applications Aim To determine the number of lines in a given grating using a laser source of light. Apparatus required He-Ne laser or semiconducting laser, grating, scale, grating stand Formula sin( ) N...

Determination of the number lines of a given grating using a laser source for display applications Aim To determine the number of lines in a given grating using a laser source of light. Apparatus required He-Ne laser or semiconducting laser, grating, scale, grating stand Formula sin( ) N lines per meter n where λ- Wavelength of the laser light used in the experiment (nm), θ - Angle of diffraction (degree) n - Order of diffraction, N-The density of lines in the grating = ––––––––––– lines/meter. Procedure 1. The grating is held normal to the laser beam at a distance D (~ 30 cm) from the screen. 2. The laser light is switched on and it is diffracted by the grating. 3. Symmetric weaker spots corresponding to different orders (n= 1,2,3,4,5,..) of diffraction will be observed around a central bright spot 4. The distances (2L) between the spots on either side of the central spot corresponding to various orders is measured and tabulated. 5. Step 4 is repeated for different values of D (~ 35 cm, 40 cm,45 cm, 50 cm). 6. The wavelength λ is calculated using the formula. 1 Tabulation Diffraction tan θ θ Mean D 2L L Sin θ N Order (L/D) -1 tan (L/D) sin θ n centimeters degrees Lines/meter cm 30 cm 35 1 40 45 50 30 35 2 40 45 50 30 35 3 40 45 50 30 35 4 40 45 50 30 35 5 40 45 50 Mean N = 2 Observations For n = 1; Mean sin θ = For n = 2; Mean sin θ = Result The density of the lines in the given grating was determined to be N = ___________________ Viva voce question 1. What is the type of the laser you used in the laboratory? 2. What is the reason for serial of light spots appearing on the measuring scale? 3. Distinguish between laser source and conventional light source. 4. Define grating element. 5. What are the requisites of good grating? 6. What is meant by diffraction of light? 7. Comment on: Grating with larger number of rulings per cm is always preferable. 8. what is the significance of the experiment 3