Electrical and Electronic Measurements – Optoelectronics Measurements MCQs

This Portion of Electrical andElectronic Measurements and Measuring instruments contains Optoelectronics Measurements MCQs (Multiple Choice Questions and Answers) / Objective Type Questions and Answers.

This Section covers below lists of topics.

1. Optical Spectrum
2. Optical transducers
3. Monochromatic Lights
4. Polarized wave shapes
5. Refraction and Refractive Index
6. Reflection, Absorption and Transmittance
7. Radiometry and Photometry
8. Laws of Illumination
9. Photometric and Radiometric Measurement System
10. Optical Sources
11. Optical Detectors
12. Light modulating Techniques
13. Visual Photometry
14. Modern Measurement Techniques
15. Fibre Optics

PRACTICE IT NOW TO SHARPEN YOUR CONCEPT AND KNOWLEDGE

1. The optical spectrum has wavelengths ranging from :

• 10 nm to 10⁶  nm
• 10 nm to 770 nm
• 370 nm to 770 nm
• 370 nm to 10⁶  nm

A. 10 nm to 10⁶  nm

2. The visible spectrum has wavelengths ranging from :

• 10 nm to 10⁶  nm
• 10 nm to 770 nm
• 370 nm to 770 nm
• 370 nm to 10⁶  nm

C. 370 nm to 770 nm

3. A certain emissive material has a work function of 2.24eV, the radiations emitted from it will have threshold length of approximately :

• 900 nm
• 600 nm
• 533.6 nm
• 527.6 nm

C. 533.6 nm

4. In order that photoelectric emission to be possible over whole of the visible spectrum of 370 nm – 770 nm, the work function of the photoemission surface should be approximately :

• 1.61 to 3.35 eV
• 1.3 to 2.25 eV
• 1.5 to 4.26 eV
• 0.231 to 5.62 eV.

A. 1.61 to 3.35 eV

5. When a light beam is made incident on a surface which is rough as compared with the wavelength of light

• Specular reflection takes place
• Diffused reflection takes place
• Absorbtion takes place
• Transmittance takes place.

B. Diffused reflection takes place

6. Radiometry refers to measurement of optical radiations

• From a wavelength of 370 nm – 770 nm
• From a wavelength of 10^-12 nm to 10⁶ nm
• From a wavelength of 10² nm to 10⁶ nm
• From a wavelength of 10 nm to 10⁶ nm

D. From a wavelength of 10 nm to 10⁶ nm

7. The response of human eyes under normal light conditions is called

• Stopopic vision and it peaks at a wavelength of 555 nm
• Stopopic vision and it peaks at a wavelength of 507 nm
• photopic vision and it peaks at a wavelength of 507 nm
• photopic vision and it peaks at a wavelength of 555 nm

D. photopic vision and it peaks at a wavelength of 555 nm

8. A light source may be considered as point source if its diameter is

• Less than 10% of the distance between it and the detector
• Less than 1% of the distance between it and the detector
• More than 10% of the distance between it and the detector
• More than 1% of the distance between it and the detector

A. Less than 10% of the distance between it and the detector

9. The units of luminous intensity are

• Lux
• Cd
• W/sr
• Cd/sr.

B. Cd

10. The unit luminance are

• nit
• lm/sr – m²
• cd/m²
• all the above.

D. all the above.

11. The errors involved in photometric measurements are of the order of

• 1%
• 1 – 5%
• 10 – 20 %
• 40 – 50 %

C. 10 – 20 %

12. The desirable properties of a laser bean are :

• It has high radiant energy
• It can be polarized
• It is monochromatic and coherent
• All the above.

D. All the above.

13. The current through a photoemissive tube depends upon

• Intensity of light incident upon it
• Colour and wavelength of incident light
• Voltage applied between cathode and anode of tube
• All the above.

D. All the above.

14. The luminous sensitivity of gas filled photoelectric cells varies between :

• 10 to 100 µA / lm
• 40 to 150 µA / lm
• 0.002 to 0.1 µA / µW
• 0.01 to 0.15 µA / µW

B. 40 to 150 µA / lm

15. A photomultiplier tube uses 10 stages. The sensitivity of each dynode of the tube is 100 µA / lm, the overall sensitivity of the photo-multiplier tube, if the gain of each stage is 2.7, is approximately :

• 2.06 A/lm
• 270 µA / lm
• 2700 µA / lm
• None of the above.

A. 2.06 A/lm

16. A photoconductive cell may be called as :

• Photoresistive cell
• Photo resistor
• Light dependent resistor
• All the above.

D. All the above.

17. The resistance of photo resistive cell

• Increases with increase in light intensity
• Remain constant irrespective of the light intensity incident upon it
• Decrease with increase in light intensity in a linear manner
• Decrease with increase in light intensity in an exponential manner.

D. Decrease with increase in light intensity in an exponential manner.

18. Photodiodes

• Do not have any response in darkness
• Have a response even in darkness
• Have a leakage current even in darkness which is called dark current that doubles for every 10°C increase in the ambient temperature that which decreases the signal to noise ratio.
• Have a leakage current even in darkness which is called dark current that doubles for every increase of 5°C in temperature and which increases the signal to noise ratio.

C. Have a leakage current even in darkness which is called dark current that doubles for every 10°C increase in the ambient temperature that which decreases the signal to noise ratio.

19. The sensitivity of a photovoltaic cell

• Is almost constant when it is short circuited
• Decrease with increase of load resistance
• Is almost negligible when the load resistance is about 10000Ω
• All the above.

D. All the above.

20. In case of measurement of intensity of test source, a standard source is used. The photometric head used when comparing two lights of different colours , is :

• Bunsen photometer head
• Constant type lummer Brodhum photometer head
• Comparison type Lummer Brodhum photometer head
• Flicker photometer head.

D. Flicker photometer head.

21. One of the combinations of materials used for optical fibers is :

• Copper core and glass cladding
• Glass core and aluminium cladding
• Glass core and plastic cladding
• Plastic core and glass cladding.

C. Glass core and plastic cladding

22. For fiber optical sensors,

• Single mode transmission is used
• Multimode transmission is used
• Both single and multimode transmission is used
• None of the above.

A. Single mode transmission is used

23. In optical fibres, if the total reflection is to take place, the following conditions must be satisfied______ Where n₁   and n₂ are respectively refractive indices of core and cladding and Φ₁  is angle of incidence.

• n₂ < n₁  and Φ₁ > cos^-1 (n₂ / n₁)
• n₁ < n₂  and Φ₁ < cos^-1 (n₂ / n₁)
• n₂ < n₁  and Φ₁ < cos^-1 (n₂ / n₁)
• n₂ > n₁  and Φ₁ > cos^-1 (n₂ / n₁)

A. n₂ < n₁  and Φ₁ > cos^-1 (n₂ / n₁)

24. In a graded index fibre, the total reflected light takes a

• Straight line path
• Parabolic path
• Elliptical path
• Circular path.

B. Parabolic path

25. The optical sensors may be classified as :

• Intensity and intrinsic types
• Interferometric and extrinsic types
• Intensity or instrinsic type and interferometric or extrinsic types
• All the above.

C. Intensity or instrinsic type and interferometric or extrinsic types