DIFFRACTION OF LIGHT. DETERMINATION of WAVELENGTH OF MONOCHROMATIC LIGHT USING DIFFRACTION GRATING

Task 1. Diffraction grating constant determination

1.1. Determine positions of diffraction maximums using scale on the screen. Enter the results into table 4.

1.2. Calculate distances between diffraction maximums as the difference between left and right readings. Enter the results into table 1.

1.3. Calculate diffraction grating constant according to the formula:

1.4. Calculate average value of diffraction grating constant:

Enter the results into table 1.

Table 1

— Calculate the random deviation of every value from mean value according to the formula:

— Determine root-mean-square deviations according to the formula:

— Calculate the absolute error of diffraction grating constant determination according to the formula:

.

where the Student’s coefficient is t_St = 2,57 (k = 3 and a = 0,95).

— Determine the fractional error of diffraction grating constant measurement according to the formula:

.

Task 2. Diffraction grating resolving power determination

Calculate amount of grating grooves N and resolving power R of diffraction grating according to the formulae:

,

Enter the results into table 2.

Table 2

Spectrum order, k	Diffraction grating width l, m	Diffraction grating constant m	Amount of grating grooves, N	Resolving power of diffraction grating, R

Conclusions

The data of laboratory work fulfilment

Pass mark Signature

Mark of laboratory work defence Signature

questions to be admitted for doing laboratory work and its defending

1. What is the essence of light diffraction phenomenon?

2. What types of diffraction do you know? Give the definition of wave front. Formulate the Huygens-Fresnel principle.

3. What is the essence of Fresnel zones method?

4. What is the essence of diffraction by a narrow slit? Deduce the formula for maximum condition for diffraction by a narrow slit.

5. What is called diffraction grating?

6. Deduce the formula for diffraction grating

7. Draw the graph of light distribution intensity under the diffraction by a narrow slit.

8. What is the resolving power of diffraction grating?

9. What is the angular and linear dispersion of diffraction grating?

10. Why does diffraction grating resolve white light into spectrum? Draw diffraction spectrum of white light.

11. What is the difference between diffraction spectrum of incandescent and mercury lamps?

12. What are the advantages of diffraction spectrum devices in comparison with the one of prism?

13. What is the essence of spectrum analysis of X-rays?

14. How is the crystalline structure of body studied with the help of diffraction?

LABORATORY WORK

Date: 2015-01-12; view: 1209