30. A beam of X-ray is incident on a sodium chloride crystal a ¼ 2:81 ˚
A
À
Á : The
first-order reflection is observed at a glancing angle 8° 35′. The wavelength of
the X-ray used is:
(a) 3.84 Å
(b) 2.84 Å
(c) 1.84 Å
(d) 0.84 Å
31. A beam of X-ray is incident on a sodium chloride crystal a ¼ 2:81 ˚
A
À
Á : The
first-order reflection is observed at a glancing angle 8° 35′. The angle for the
second order of reflection is:
(a) 7.4°
(b) 17.4°
(c) 27.4°
(d) 37.4°
32. A beam of X-ray of wavelength 0.440 Å is used to study the cube face of a
rock-salt crystal (d = 2.814 Å). The first-order reflection is observed at a
glancing angle of:
(a) 4° 29′
(b) 6° 29′
(c) 8° 29′
(d) 10° 29’
33. A beam of X-ray of wavelength 0.440 Å is used to study the cube face of a
rock-salt crystal (d = 2.814 Å). The third-order reflection is observed at a
glancing angle of:
(a) 33° 34′
(b) 23° 34′
(c) 13° 34′
(d) 3° 34’
34. A beam of X-ray having wavelengths in the range 0:2 ˚
A to 1 ˚
A is allowed to
incident at an angle of 9° with the cube face of rock-salt crystal d ¼ 2:814 ˚
A
À
Á :
For the diffracted beam, the maximum allowed value of the wavelength is:
(a) 0.88 Å
(b) 0.77 Å
(c) 0.66 Å
(d) 0.55 Å
7.4 Other Diffraction Methods
293