Note: For systematic learning, you can check the index page of the Instruments in Forensic Science. Here, we listed all the MCQs based on the NTA UGC syllabus.
1. Numerical aperture of the objective lens of a microscope is equal to the following:
- 1/2 n sin θ
- 0.61λ /sin θ
- n sin θ
- None of these
Answer and Explanation
Answer: (3) n sin θ
Explanation: Numerical aperture states the power of a microscope objective to gather light and resolve a sharp specimen detail at a fixed object distance.
Numerical Aperture (NA) = η • sin(α)(1).
Where,
-> α equals one-half of the objective’s opening angle
-> η is the refractive index of the immersion medium (η = 1 for air; η = 1.51 for oil or glass).
Therefore, theoretically, the highest angular aperture would be 180 degrees.
2. For comparison of bullets, following microscope is used for identification?
- Fluorescent microscope
- Polarizing microscope
- Neuron microscope
- Comparison microscope
Answer
Answer: (4) Comparison microscope
3. Let f = focal length of a convex lens, p = distance of the object from the lens, q = distance of the image from the lens. Then which one of the following is true for photomicrography?
- p > 2f, f < q < 2f
- p = 2f, q = 2f
- p > 2f, q > 2f
- f < p < 2f, q > 2f
Answer and Explanation
Answer: (4) f < p < 2f, q > 2f
Explanation: For photomicrography (taking close-up photos using a microscope):
-> The microscope’s objective lens acts like a magnifying glass (convex lens).
-> The specimen (like a tiny organism) is the object we’re looking at.
Here’s how the microscope works:
-> The specimen is placed a little beyond the lens’s main focus point but not too far. This is represented as f < p < 2f.
-> The lens then creates a clear, enlarged, and upside-down image of the specimen. This image appears even further away, represented as q > 2f.
So, in simple terms for photomicrography:
-> The specimen is placed just a bit beyond the main focus of the lens.
-> The lens shows us a clear and enlarged image that appears quite distant.
This behavior is specific to how microscopes work and might differ from the usual behavior of convex lenses in other situations.
In the general case, for a convex lens (not specific to photomicrography):
- Object at Infinity: Image is formed at the focal point (f).
- Object beyond 2f (p > 2f): Image is formed between f and 2f (f < q < 2f).
- Object at 2f (p = 2f): Image is also at 2f (q = 2f).
- Object between f and 2f (f < p < 2f): Image is formed beyond 2f (q > 2f).
4. One of the major limitations of a conventional light microscope is, shallow depth of the field, overcome by applying an adjustable beam of highly intense light to the area under illumination in
- Confocal Microscope
- Laser Doppler Microscope
- Deepfield Microscope
- Ultraviolet Microscope
Answer
Answer: (3) Deepfield Microscope
5. Assertion (A): The major limitations of the conventional optical microscope are limited resolution, restricted depth of field, and poor contrast.
Reason (R): Conventional optical microscope is characterized by a sequential processing system.
- Both (A) and (R) are correct
- Both (A) and (R) are incorrect
- (A) is correct and (R) is incorrect
- (A) is incorrect and (R) is correct
Answer and Explanation
Answer: (3) (A) is correct and (R) is incorrect
Correct Reason: Conventional optical microscope is characterized by the parallel processing system i.e. simultaneously image formation onto the retina of the eye.
6. Which of the following is true for a compound microscope?
- Object placed just beyond lower focal point of objective lens which forms enlarged real image within lower focal plane of ocular.
- Object placed within lower focal point of objective lens which forms enlarged real image within lower focal plane of ocular.
- Object placed just beyond lower focal point of objective lens which forms enlarged real image beyond lower focal plane of ocular.
- Object placed within lower focal point of objective lens which forms enlarged real image beyond lower focal plane of ocular.
Answer
Answer: (1) Object placed just beyond the lower focal point of the objective lens which forms enlarged real image within the lower focal plane of ocular
7. Many forensic scientists keep a hand magnifier with them for preliminary examination of some exhibits, such as tattooing around a gun-shot hole in clothes. In connection with the hand magnifier, which of the following statements is correct?
- The object is within ‘F’ of the lens and it forms large virtual image.
- The object lies between ‘F’ and ‘2F’ and real image is formed at a distance greater than ‘2F’.
- The object is at ‘3F’ and the image is also formed at ‘P’.
- All are correct.
Where ‘F’ stands for the focal length of the hand magnifier.
Answer and Explanation
Answer: (1) The object is within ‘F’ of the lens and it forms large virtual image.
Explanation: If a hand lens placed near an object, within F, it forms large virtual image.
8. Exciter Filter is used in
- Polarising Microscope
- Scanning Electron Microscope
- Stereoscopic microscopic
- Fluorescent Microscope
Answer and Explanation
Answer: (4) Fluorescent Microscope
Explanation: Exciter filter is used in a fluorescent microscope which permits only selected wavelengths from the illuminator to pass through the specimen. In short, it is a high-quality wavelength selection filter.
9. For photomicrography, the position of an object is:
- Beyond 2F of convex lens
- At 2F of convex lens
- Between F and 2F of the lens
- Less than F of the lens
Answer
Answer: (3) Between F and 2F of the lens
10. Polarising microscope is useful in the identification of the following:
- Paint
- Soil
- Fibers
- Paper
Answer and Explanation
Answer: (3) Fibers
Explanation: A polarizing microscope is used to identify trace evidence such as fibers, hairs, paints, and glass fragments. But majorly the fibers. As it has both the option paint and fiber, so, fiber is the correct answer.
11. Analyser is used in:
- Polarising microscope
- Stereoscopic microscope
- Fluorescent microscope
- Comparison microscope
Answer and Explanation
Answer: (1) Polarising microscope
Explanation: In general, there are two main components of a polarising microscope i.e. polarizer and analyzer.
-> Polarizer is used to filter light waves in order to generate polarization of light.
-> Analyzer acts as a second polarizer.
12. The Numerical Aperture of oil immersion type objective lens of microscope varies between:
- 0.2-0.5
- 0.5-0.8
- 0.8-1
- 1-1.4
Answer and Explanation
Answer: (4) 1-1.4
Explanation: In general, most oil immersion objectives have a maximum numerical aperture of 1.4, while the most common numerical apertures range from 1.0 to 1.35.
Note: Jump to the main page of Instrumentation MCQs in Forensic Science.
What is Q7 ? The answer doesn’t match the options.
I changed the question. Check the updated question
For Q3, aren’t all options except 3 right?
I added more explanations and references for your query
In Q3 option 2 is also correct right, when the object(p) is at 2f of a lens then, it forms image(q) at 2f of the other side of the lens right
Yes, you’re correct. But answer still remains the same as the question specific to photomicrography. I added more explanation to the answer.
Que no 10 correct ans as per ans key ..?
Fiber