1: In a young double slit experiment the separation of the slits is 1 mm and red light of wavelength 620 nm is falling on it. Determine the distance between the central bright band and the fifth bright fringe on the screen which is 3m away from the slit. (9.3 mm)

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2: Two parallel slits are illuminated by light of two wavelengths, one of which is 5.8 x 10⁻⁷ m. On the screen the fourth dark line of the known wavelength coincides with the fifth bright line of the light of unknown wavelength. Find the unknown wavelength. (5.2 x 10⁻⁷ m Book Answer is wrong.) (Correct Ans. is 4.1 x 10⁻⁷ m)




3: When the movable mirror of a Michelson interferometer is moved 0.1 mm. How may dark fringes pass through the reference point, if light of wavelength 580 nm is used? (345 fringes)

4: A soap film has a refractive index of 1.40. How thick must the film be, if it appears black, when mercury light of wavelength 546.1 nm falls on it normally? (1.95 x 10⁻⁷ m) 

5: A diffraction grating has 5000 lines per centimeter. At what angle does the second order spectrum of the sodium yellow light of wavelength 589 nm occur? (0.36) 

6: Light is incident normally on a grating which has 250 lines / mm. Find the wavelength of spectral line for which the deviation in second order is 12°  (λ = 4158 x 10⁻¹⁰ m)




7: In a certain X-rays diffraction experiment the first order image is observed at an angle of 5° for a crystal plane spacing of 2.8 x 10⁻¹⁰ m. What is the wavelength of X-rays used? (0.49 X 10⁻¹⁰ m) 

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8: An X-ray beam of wavelength 0.48 x 10⁻¹⁰ m is used to get Brag reflection from a crystal at an angle of 20° for the first order maxima. What are the possible layer plane spacing which give rise to this maximum? (0.70 x 10⁻¹⁰ m) 




9: The spacing of one set of crystal planes in NaCl table salt) is d = 0.282 nm. Monochromatic beam of x-rays produces a Bragg maximum when its glancing angle with these planes θ = 7° .  Assuming this is a first order maximum (m=1). Find the wavelength of the X-rays.  (0.069 nm) 

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