Chapter 16 Pretest Interference and Diffraction

1. When monochromatic light is reflected from a thin transparent film, A) constructive interference occurs when the film is one-half wavelength thick, B) a bright spot appears at the half- wave point, C) destructive interference occurs when the film is one-fourth wavelength thick, D) a dark spot appears at the half-wave point.

2. For a thin film bounded on both sides by a medium of lower index of refraction, maximum constructive interference occurs if the optical path difference is: A) /4, B) /2, C) ¾, D).

3. For high resolution in optical instruments, the angle between resolved objects should be: A) as small as possible, B) as large as possible, C) 1.22°, D) 45°.

4. Interference effects observed in the early 1800s were instrumental in supporting a concept of the existence of which property of light? A. polarization B. particle nature C. wave nature D. electromagnetic character

5. For stable interference to occur, the phase difference must be: A. V/C B. c C. ½ D. constant

6. At the first dark band in a single-slit interference pattern, the path lengths of selected pairs of wavelets differ by: A. one wavelength B. more than one wavelength C. one-half wavelength D. less than half of one wavelength

7. Which of the following is a device that produces an intense, nearly parallel beam of coherent light? A. spectroscope B. telescope C. laser D. diffraction grating

1. Why are the interference effects observed in light reflected by thin films the reverse of those normally expected?

There is a phase inversion where the medium beyond is of a higher index of refraction.

2. Calculate to the nearest 0.1° the diffraction angle of the first-order image produced by a grating ruled 5000 lines/cm illuminated with monochromatic light having a wavelength of 295 nanometers.

 = d sin  /m 295 X  = (1/5000)(1/100) sin  /1  = 8.5º

3. The angle between the first order maximum and zeroth order maximum for monochromatic light of 2300 nm is 27°. Calculate the number of lines per centimeter on this grating.

 = d sin  /m 2300 X  = d sin27º /1 d = x m/line 1/(5.066 x )(1/100) 1974 lines/cm

4. Monochromatic light from a helium-neon laser ( = nm) shines at a right angle onto the surface of a diffraction grating that contains 630,692 lines/m. Find the angles at which one would observe the first-order and second-order maxima.

 = d sin  /m X  = 1/(630,692) sin  /1  = 23.5º

 = d sin  /m X  = 1/(630,692) sin  /2  = 53.0º