Optical Sources, Detectors and Interferometry - Communication and Optical Instrumentation - Instrumentation Engineering Previous Year Questions

1

2009 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2009

A mass spectrometer is to be used to resolve peaks corresponding to CO⁺ and N₂⁺. The atomic masses are ¹²C = 12.0000, ¹⁶O = 15.9949, and ¹⁴N = 14.0031 amu. The resolving power of the mass spectrometer should be at least

A

250

B

350

C

2500

D

3500

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2

2009 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2009

The operating voltage of an X-ray tube is changed from 40 kV to 50 kV. The resulting change in the shortest wavelength generated is

A

+20%

B

-20%

C

+25%

D

-36%

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3

2009 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2009

The central wavelength of the source is

A

540 nm

B

632.8 nm

C

667 nm

D

720 nm

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4

2009 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2009

The spectral width of the source \(\Delta\lambda\) is approximately

A

0.0056 nm

B

0.0100 nm

C

0.0500 nm

D

0.1000 nm

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5

2010 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2010

A beam of unpolarized light is first passed through a linear polarizer and then through a quarter-wave plate. The emergent beam is

A

unpolarized

B

linearly polarized

C

circularly polarized

D

elliptically polarized

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6

2013 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2013 [Session 1]

Measurement of optical absorption of a solution is disturbed by the additional stray light falling at the photo-detector. For estimation of the error caused by stray light the following data could be obtained from controlled experiments. Photo-detector output without solution and without stray light is 500 μW. Photo-detector output without solution and with stray light is 600 μW. Photo-detector output with solution and with stray light is 200 μW. The percent error in computing absorption coefficient due to stray light is

A

12.50

B

31.66

C

33.33

D

94.98

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7

2015 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2015

The resolving power of a spectrometer consisting of a collimator, a grating and a telescope can be increased by (A) increasing the angular magnification of the telescope (B) increasing the period of the grating (C) decreasing the period of the grating (D) decreasing the slit-width of the collimator

A

increasing the angular magnification of the telescope

B

increasing the period of the grating

C

decreasing the period of the grating

D

decreasing the slit-width of the collimator

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8

2025 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2025

A schematic of a Michelson interferometer, used for the measurement of refractive index of gas, is shown in the figure. The transparent chamber is filled with a gas of refractive index \(n_g\), where \(n_g \neq 1\), at atmospheric pressure. If a 532 nm laser beam produces 30 interference fringes on the screen, then the number of fringes produced by a 632.8 nm laser beam will be ____(rounded off to one decimal place).
Note: Assume that the effect of beamsplitter width is negligible. The setup is placed in air medium with refractive index equal to 1.

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9

2007 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2007

The dispersion in an X-ray diffractometer, \(\frac{d\theta}{d\lambda}\), is given by the expression

A

\(\frac{m}{2d \cos \theta}\)

B

\(\frac{m}{2d \sin \theta}\)

C

\(2d \sin \theta\)

D

\(2d \cos \theta\)

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10

2008 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2008

For radioisotope imaging, an Anger camera is fitted with a parallel hole collimator. If the thickness of the collimator is increased, the camera

A

resolution and sensitivity will increase

B

resolution and sensitivity will decrease

C

resolution will increase and sensitivity will decrease

D

resolution will decrease and sensitivity will increase

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11

2008 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2008

A laser light with a wavelength of 633 nm is passed through 1 cm length of tissue and 2 cm length of glass. The refractive indices of tissue and glass are 1.33 and 1.5 respectively. The velocities of laser light in the tissue and in the glass are in the ratio of

A

1.33 : 0.75

B

1.33 : 3.0

C

1.33 : 1.5

D

1.5 : 1.33

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12

2008 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2008

An X-ray tube is operated at 80 kV anode voltage. In order to filter the low intensity X-rays, a 2.5 mm thick aluminum filter is used. It is given that at 80 kV anode voltage, the mass attenuation coefficients and densities of aluminum are \(0.02\,m^2kg^{-1}\) and \(2699\,kgm^{-3}\) respectively and for copper these are \(0.075\,m^2kg^{-1}\) and \(8960\,kgm^{-3}\) respectively. If a copper filter is to replace the aluminum filter with the same filtering effect, the thickness of the copper filter should be

A

0.2 mm

B

0.66 mm

C

1.5 mm

D

5 mm

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13

2008 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2008

A tissue with a refractive index 1.33 is introduced in one of the light paths of a Michelson interferometer operating with a monochromatic coherent light source of wavelength 589 nm. After the introduction of a tissue sample of thickness Δt, the fringe pattern is observed to shift by 50 fringes. If the thickness is 2Δt, the fringe pattern will shift by

A

25 fringes

B

50 fringes

C

100 fringes

D

200 fringes

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14

2008 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2008

In this process, helium molecules

A

play no role

B

produce laser light

C

give energy to neon molecules

D

absorb energy from neon molecules

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15

2008 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2008

Wavelength of laser light generated in this process is

A

61.6 nm

B

66.4 nm

C

633.8 nm

D

650.3 nm

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16

2017 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2017

Quantum efficiency of a photodiode (ratio between the number of liberated electrons and the number of incident photons) is \(0.75\) at \(830 \text{ nm}\). Given Planck's constant \(h = 6.624 \times 10^{-34} \text{ J}\), the charge of an electron \(e = 1.6 \times 10^{-19} \text{ C}\) and the velocity of light in the photodiode \(c_m = 2 \times 10^8 \text{ m/s}\). For an incident optical power of \(100 \text{ }\mu\text{W}\) at \(830 \text{ nm}\), the photocurrent in \(\mu\text{A}\) is __________.

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17

2018 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2018

An optical pulse containing \(6 \times 10^6\) photons is incident on a photodiode and \(4.5 \times 10^6\) electron-hole pairs are created. The maximum possible quantum efficiency (in %) of the photodiode is ____.

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18

2018 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2018

A Michelson Interferometer using a laser source of wavelength \(\lambda_0 = 500\) nm, with both the mirrors (\(M_1\) & \(M_2\)) fixed and positioned equidistant from the splitter/combiner is shown in the figure. When a dielectric plate of refractive index \(n = 1.5\), of thickness \(t\), is placed in front of the mirror \(M_2\), a dark fringe is observed on the detector. When the dielectric plate is removed without changing the position of the mirrors \(M_1\) & \(M_2\), a bright fringe is observed on the detector. The minimum thickness \(t\) (in nm) of the dielectric is ______.

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19

2019 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2019

A pulsed laser emits rectangular pulses of width 1 nanosecond at a repetition rate of 1 kHz. If the average power output is 1 mW, the average power over a single pulse duration, in watts, is

A

1

B

10

C

100

D

1000

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20

2019 · Instrumentation Engineering · Communication and Optical Instrumentation · Optical Sources, Detectors and Interferometry

Instrumentation Engineering (IN) 2019

Consider a Michelson interferometer as shown in the figure below. When the wavelength of the laser light source is switched from 400 nanometer to 500 nanometer, it is observed that the intensity measured at the output port P goes from a minimum to a maximum. This observation is possible when the smallest path difference between the two arms of the interferometer is ____ nanometer.

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