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Chapter Nine – Physical Optics

Optics deals with light and light is a type of energy.this chapter is about light and its properties about its wave nature.wavefront is a surface on which all the points have same phase.spherical wavefronts are formed if disturbance propagate in all directions.wavelength is the distance between two consecutive wavefronts.

Interference is the phenomenon in which two or more waves interfere each other and form a resultant wave.if the amplitude of resultant wave is greater than either of the individual waves, interference is called constructive interference and if the amplitude of resultant is less than either of the individual waves,interference is destructive interference.the property of bending of light around obstacles is called diffraction.

Q 9.1: Light of wavelength 546nm is allowed to illuminate the slits of Young’s experiment. The separation between the slits is 0.10 mm and the distance of the screen form the slits where interference effects are observed is 20 cm. At what angle the first minimum will fall? What will be the linear distance on …

Q 9.2: Calculate the wavelength of light illuminates two, slits 0.5mm apart and produces an interference pattern on a screen placed 200 cm away from the slits. The first bright fringe is observed at distance of 2.4 mm from the central bright image.

Q 9.3: In a double slit experiment the second order maximum occurs at an angle of 0.25 degree. The wavelength is 650 nm. Determine the slit separation.

Q 9.4: A monochromatic light of wavelength 588nm is allowed to fall on the half silvered plate G1, in the Michelson interferometer. If mirror M1 is moved through 0.233mm, how many fringes will be observed to shift?

Q 9.5: A second order spectrum is formed at an angle of 38 degree when light falls normally on a diffraction grating having 5400 lines per centimeter.Determine wavelength of the light used.

Q 9.6: A light is incident normally on a grating, which has 2500 lines per centimeter. Compute the wavelength of a spectral line for which the deviation in second order is 15 degree.

Q 9.7: Sodium light of wavelength 589 nm is incident normally on a grating having 3000 lines per centimeter. What is the highest order of the spectrum obtained with this grating?

Q 9.8: Blue light of wavelength 480 nm illuminates a diffraction grating. The second order image is formed at an angle of 30 degree from the central image. How many lines in a centimeter of the grating have been ruled?

Q 9.9: X-rays of wavelength 0.15nm are observed to undergo a first order reflection at a Bragg angle of 13.3 degree from a quartz (SiO2) crystal. What is the interplanar spacing of the reflecting planes in the crystal?

Q 9.10: X-ray beam of wavelength undergoes a first order reflection from a crystal when its angle of incident to a crystal face is 26.5 degree, and an X-ray beam of wavelength 0.097nm undergoes a third order reflection when its angle of incidence to that face is 60 degree. Assuming that the two beams reflect …