# MCQ on Diffraction in Wave Optics

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## MCQ on Diffraction in Wave Optics

MCQ on Diffraction in Wave Optics, Multiple Choice Questions on Diffraction in Wave Optics, Diffraction MCQ, Wave Optics MCQ, Engineering MCQ, Objective Questions with answers on Diffraction in Wave Optics, Engineering Physics MCQ

### Multiple Choice Questions

Q.1. The condition for observing Fraunhoffer diffraction from a single slit is that the light wavefront on the slit should be:

• Spherical
• Cylindrical
• plane
• elliptical

Q.2. Maximum number of orders available with a grating is:

• independent of grating element
• directly proportional to grating element
• inversely proportional to grating element
• directly proportional to wavelength

Answer: inversely proportional to grating element

Q.3. In Fraunhoffer’s diffraction at double slit, on increasing the slit-width:

• central peak will become sharper
• fringe spacing will decrease
• more interference maxima fall within the central envelope
• pattern remains same

Answer: central peak will become sharper

Q.4. In a grating if (e + d) < 2λ then the maximum number of order will be:

• greater than 3
• less than 2
• equal to 0.5
• less than 1 and greater than 2

Q.5. Dispersive power of a grating is:

• inversely proportional to the order n
• inversely proportional to the grating element (e + d)
• inversely proportional to angle of diffraction θ
• none of these

Answer: inversely proportional to the grating element (e + d)

Q.6. If N is the total number of rulings on the grating, n is the order of spectrum and λ is the wavelength of light used, then resolving power of grating is:

• $Nn\lambda$
• $n\lambda$
• $N\lambda$
• $\frac{n\lambda }{N}$

Answer: $N\lambda$

Q.7. In a diffraction experiment, the size of obstacle in path of light should be of the order of:

• 1 mm
• 0.1mm
• 10-4 mm
• 1 cm

Q.8. In Fraunhoffer diffraction at a single slit the intensity of the first subsidiary maxima is:

• 4.5% of the principal maxima
• 22% of the principal maxima
• 45% of the principal maxima
• 2.2% of the principal maxima

Answer: 4.5% of the principal maxima

Q.9. If the width of a grating element is less than twice the wavelength of light, then which order is possible?

• only first order
• no spectrum is visible
• first and second order
• none of these

Q.10. Consider Fraunhoffer diffraction pattern obtained with a single slit at normal incidence. At the angular position of the first diffraction minimum, the phase difference (in rad) between the wavelets from the opposite edges of the slit is:

• π/4
• π/2
• π

Q.11. A grating which would be more suitable for constructing a spectrometer for the visible and ultraviolet regions, should have

• 100 lines/cm
• 1000 lines/cm
• 10,000 lines/cm
• 106 lines/cm