13-04-2012, 11:16 AM
Engineering Physics question paper
Q1. With the help of a neat diagram show an experimental arrangement to produce Newton’s
rings by reflected sodium light. Prove that in reflected light the diameter of dark ring is
proportional to the square root of the natural number.
Q.2 Explain analytically the colours of thin films. Why the colours are in reflected and
transmitted light are complimentary?
Q3. In Newton’s ring experiment, the diameter of 10th ring changes from 1.50 cm to 11.30 cm
when a liquid is introduced between the lens and the plate. Calculate the refractive index of the
liquid.
Q4 When the mirror of Michelson’s interferometer is moved by a 0.05 mm, a shift of 200
fringes is observed. What is the wavelength of light used. ?
Q5. The wavelength of the two components of D lines of sodium are 5890 Å and 5896 Å,
respectively. Through what distance the mirror of Michelson’s interferometer be moved to obtain
two conservation positions of distinction?
Q6. In an experiment for determining the refractive index of a glass plate with Michelson’s
interferometer a shift of 100 fringes is observed on introduction of the plate. If the wavelength of
light used is 4000 Å and the thickness of the glass plate is 0.2 mm. Calculate the refractive index
of the glass.
Q7. In Newton’s ring experiment, the diameter of the 4th and 12th rings are 0.4 cm and 0.7 cm
respectively. Find the diameter of the 20th dark ring
Q8. Newton’s rings are formed by reflection in an air film between a plane surface and a
spherical surface of radius of curvature 50 cm and it is noticed that the center of the ring system
is bright. If the diameter of the 3rd bright ring is 0.0181 cm and the diameter of 23rd bright ring is
0.501 cm. What is the wavelength of light used? What conclusion would be drawn from the fact
that the center of the ring system is bright?
Q9. Newton’s rings are observed in reflected light of = 5.9 x 10-5 cm. The diameter of 10th dark
ring is 0.05 cm. Find the radius of curvature of the lens and the thickness of the air film.
Q10. In Newton’s ring set up, suppose the plano convex lens is slightly raised above the plane
(glass). What change do you expect and why?
Q11. Newton’s ring arrangement is used with a light source of wavelengths 1 = 8000Å and 2
= 7000Å and it is found that nth dark ring due to 1 , coincide with (n+1)th dark ring due to 2. If
radius of curvature of curved surface of the lens is 80 cm, then find the diameter for the nth dark
ring for 1.
Q12. Explain the meaning of Fresnel half period zones. Why are they called so? What is the
phase difference between wavelets from successive half period zones? Prove that the area of a
half-period zone on a plane wave front is independent of the order of the zone.
Q13. Discuss the phenomena of Fraunhoffer diffraction at a single slit and show that the relative
intensities of the successive maximum are nearly
1:4/9 2: 4/25 2 : 4/49 2.
Q14. Newton’s rings are observed in reflected light of = 5.0 x 10-5 cm. The radius of 20th dark
ring is 0.02 cm. Calculate the radius of curvature of the lens.
Q15. Discuss the phenomenon of interference in thin films. Obtain the condition for maxima and
minima. Show that the interference pattern in the reflected and transmitted system is
complementary.