December 2007

Sree Narayana Guru College of Engineering and Technology, Payyanur
First series test - December 2007


EN2K 102: ENGINEERING PHYSICS

Time: 11/2Hours Marks: 50

Part A: Answer all questions

1 Explain why the center of Newton’s rings is dark in the reflected system.
2 Explain Fresnel’s and Fraunhoffer diffraction.
3 Describe how half shade polarimeter is used to determine the specific rotation of glucose.
4 Write briefly how elliptically polarized light can be detected.
(4x5=20 Marks)

Part B: Answer two questions

5 (a) Explain the phenomenon of interference in thin films. Obtain expressions for constructive and destructive interference in the reflected system. (10 Marks)

(b) A diffraction grating used at normal incidence gives a green line (5400Å) of a certain order superimposed on a violet line (4050Å) of the next order. If the angle of diffraction is 30 degrees, find the number of lines per meter of the grating. (5 Marks)

OR

6 (a) Explain how the refractive index of a liquid can be determined by forming wedge shaped film. Derive the formula used. (10 Marks)
(b) Light of wavelength 6000Å falls on a grating normally. Two adjacent principal maxima occur at 120 and 15.060 respectively. Calculate the grating element. (5 Marks)

7 (a) Explain the crystal structure of calcite. Explain the method of construction of nicol prism from a calcite crystal. (10 Marks)
(b)A column of sugar solution 0.2m long rotates the plane polarization through 170. If the specific rotation of sugar solution is 0.0116 rad/m/kg/m3. Find the amount of sugar in unit volume of the solution. (5 Marks)

OR

8 (a) Write a brief note on half wave plate and quarter wave plate. Write any five applications of polarized light (10 Marks)

(b) A sugar solution in a tube of length 20 cm produces optical rotation of 130. The solution is then diluted to one third of its previous concentration. Find the optical rotation produced by 30 cm long tube containing the diluted solution. (5 Marks)