At the second minimum adjacent to the central maximum of a single-slit diffraction pattern the Huygens wavelet from the top of the slit is 180° out of phase with the wavelet from: 

A. a point one-fourth of the slit width from the top 

B. the midpoint of the slit 

C. a point one-fourth of the slit width from the bottom of the slit 

D. the bottom of the slit 

E. none of these 

As more slits with the same spacing are added to a diffraction grating the lines: 

A. spread farther apart 

B. move closer together 

C. become wider 

D. becomes narrower 

E. do not change in position or width

In a Young’s double-slit experiment the center of a bright fringe occurs wherever waves from the slits differ in the distance they travel by a multiple of: 

A. a fourth of a wavelength 

B. a half a wavelength 

C. a wavelength 

D. three-fourths of a wavelength 

E. none of the above

Bragg’s law for x-ray diffraction is 2d sin θ = mλ, where the quantity d is: 

A. the height of a unit cell 

B. the smallest interatomic distance 

C. the distance from detector to sample 

D. the distance between planes of atoms 

E. the usual calculus symbol for a differential

Waves from two slits are in phase at the slits and travel to a distant screen to produce the second minimum of the interference pattern. The difference in the distance traveled by the waves is: 

A. half a wavelength 

B. a wavelength 

C. three halves of a wavelength 

D. two wavelengths 

E. five halves of a wavelength

The spacing between adjacent slits on a diffraction grating is 3λ. The deviation θ of the first order diffracted beam is given by:

A. sin(θ/2) = 1/3 

B. sin(θ/3) = 2/3 

C. sin(θ)=1/3 

D. tan(θ/2) = 1/3 

E. tan(θ)=2/3

The intensity at a secondary maximum of a single-slit diffraction pattern is less than the intensity at the central maximum chiefly because: 

A. some Huygens wavelets sum to zero at the secondary maximum but not at the central maximum 

B. the secondary maximum is further from the slits than the central maximum and intensity decreases as the square of the distance 

C. the Huygens construction is not valid for a secondary maximum 

D. the amplitude of every Huygens wavelet is smaller when it travels to a secondary maximum than when it travels to the central maximum 

E. none of the above

A liquid of refractive index n = 4/3 replaces the air between a fixed wedge formed from two glass plates as shown. As a result, the spacing between adjacent dark bands in the interference pattern:

A. increases by a factor of 4/3 

B. increases by a factor of 3 

C. remains the same 

D. decreases to 3/4 of its original value 

E. decreases to 1/3 of its original value

Light of wavelength is normally incident on some plane optical device. The intensity pattern shown is observed on a distant screen (θ is the angle measured from the normal of the device). The device could be:

A. a single slit of width W 

B. a single slit of width 2W 

C. two narrow slits with separation W 

D. two narrow slits with separation 2W 

E. a diffraction grating with slit separation W

Which of the following is true for Bragg diffraction but not for diffraction from a grating? 

A. Two different wavelengths may be used 

B. For a given wavelength, a maximum may exist in several directions 

C. Long waves are deviated more than short ones 

D. There is only one grating spacing 

E. Maximum occur only for particular angles of incidence