This set of Solid State Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Diffraction”.
1. Diffraction refers to the phenomenon that occurs when _________ encounters an obstacle or a slit.
a) Liquid particles
b) Gaseous particles
c) Electric field
Explanation: Diffraction is a phenomenon that take place when waves encounters an obstacle or a slit. It is defined as the bending of the light around the corner of an obstacle.
2. Which of the following statement is true for the optical grating?
a) It gives 1 dimensional analogue of the 2 dimensional process
b) It gives 2 dimensional analogue of the 3 dimensional process
c) It gives 3 dimensional analogue of the 1 dimensional process
d) It gives 1 dimensional analogue of the 3 directional process
Explanation: Optical grating is a system by which we understand the diffraction of light, so it gives a one dimensional analogue of the three dimensional process that occurs in crystals.
3. In optical grating, what is the range of the separation of the lines?
a) 10 A˚
b) 100 A˚
c) 10000 A˚
d) Greater than 10000 A˚
Explanation: An optical grating may consist of a piece of glass on which have been ruled a large number of accurately parallel and closely spaced lines. The separation of the lines should be a little larger than the wavelength of light, i.e. 10000A˚.
4. Lines on the glass in optical grating act as________
b) Concentration factor
c) Secondary source of light
d) Primary source of light
Explanation: A piece of glass without the lines would simply transmit the light, but in the grating the lines act as secondary point (or, rather, line) sources of light and radiate light in all directions.
5. Which of the following phenomenon occur when the waves originate from each line source in the optical grating?
a) Magnetic flux
Explanation: Interference occurs between the waves when they originate from each line source. In certain directions, adjacent beams are in phase with each other and constructive interference occurs to give a resultant diffracted beam in that direction.
6. Which of the following equation is used for the constructive interference in optical grating?
a) a tanα=nλ
b) a cotα=nλ
c) a sinα=nλ
d) a secα=nλ
Explanation: This equation gives the conditions under which constructive interference occurs and relates the spacing of the grating to the light wavelength and the diffraction order, n. Hence, depending on the value of a sinα, one or more diffraction orders, corresponding to n=1,2, etc, may be observed.
7. What is the condition for the first order diffracted beam, in the optical grating?
a) a tanα=λ
b) a sinα=2λ
c) a sinα=λ
d) a sinα=3λ
Explanation: The separation of the lines on the grating must be of the same order of magnitude as but larger than the wavelength of the light. The condition for the first order diffracted beam to occur is a sinα=λ. The maximum value of sinα=1, corresponding to α=90˚.
8. For the first order diffraction in the optical grating which of the following condition is required for the constructive interference?
Explanation: The condition for the first order diffraction in the optical grating is that Sinα=λ. In order to observe first order diffraction, sinα<1 and therefore α>λ. If α<λ only the zero order direct beam is observable.
9. In the optical grating system if α>>λ, for the constructive interference which of the following phenomenon takes place?
a) Refraction of light
b) Deflection continuum
c) Diffraction continuum
d) Refraction continuum
Explanation: In the optical grating system, if α>>λ individual diffraction orders (n=1, 2, 3, etc) are close together as to be unresolved and effectively, a diffraction continuum results. This is because for large values of a sinα and hence, λ must be very small.
10. The condition for the constructive of an optical grating is that ______________
a) The lines are perpendicular to each other
b) The lines are parallel each other
c) The lines intersect each other
d) The lines crosses each other
Explanation: One of the condition that is observed in the construction of an optical grating is that the lines should be accurately parallel. If this were not so, α would vary over the grating and the diffraction spectra would be blurred or irregular and of poor quality generally.
Sanfoundry Global Education & Learning Series – Solid State Chemistry.
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