Optics Answers

 A ray of light is incident in water on a plane water-glass boundary. The angle of incidence is 30°.

   Calculate the angle of deviation.

  A ray of light is incident in air at an angle of 40° to the normal to one face of a 60° glass prism.

   Calculate the angle through which the ray has been deviated by the time it emerges from the prism.

   A narrow parallel pencil of monochromatic light is incident on a plane boundary between air and

glass. Describe the phenomena which occur as the angle of incidence of the light is progressively

increased from 0° to 90°, (a.) in the air, (b.) in the glass.                    

A parallel beam of light of wavelength 5.5 × 10^-7m in air is incident on the slits in Young's double slit experiment. A thin film of transparent plastic of refractive index 1.48 and thickness

5.2µm is placed over one of the slits.

(i.) Determine the increase in the optical path of the light passing through the thin film.

(ii.) Determine the number of fringes by which the central fringe is displaced.

(iii.) Explain how the fringe spacing would change if:

     • The slit separations were increased.

     • The slit-screen distances were increased.

(a ) Differentiate between interference and diffraction of light.

(a ) What is meant by a coherent light source?

(b) Describe how you would determine the wavelength of monochromatic light using Young's

double slit. Your account should include a diagram, observations, precautions, and how you use the

observations to reach conclusions.

A beam of parallel light is incident normally on a diffraction grating having 550 lines per mm. A

 telescope is used to observe the second order in the spectrum. Calculate the angular separation in radians of two spectra lines of wavelengths 559nm and 563nm.

 A laser is used to produce young fringes with slits separated by 0.50mm. The screen is 1.0m

     from the slits and 10 fringe separations occupy 12.5mm. What is the wavelength of the laser light?

     State the advantage of using light from a laser. 

 (a.) Diffraction and interference are phenomena exhibited by waves. State clearly the differences

     between these two phenomena.

When a thin film of transparent plastic is placed over one of the slits in Young's double slit

     experiment, the central fringe is displaced by 4.5 fringes. The refractive index of the material is 1.48

    and the wavelength of the light in air is 5.5 × 10^-7 m.

    (i.) By how much does the film increase the optical path?

    (ii.) What is the thickness of the film?

    (iii.) What would be observed if the material had a thickness of 1.00mm? Explain.