Physics

Optical Instruments and Human Eye

416 Questions

Optical instruments and the human eye explore how lenses and mirrors are used to magnify and resolve images. Key topics include the magnifying power of astronomical telescopes, compound microscope configurations, and hyperfocal distance calculations. These physics concepts are vital for general science competitive exams.

Telescope magnifying powerCompound microscope lensesHyperfocal distance calculationHuman eye resolutionSpherical mirror magnification

Optical Instruments and Human Eye Questions

Multiple choice

Depth of field in a compound light microscope, refers

  1. to the thinness of the plane of focus

  2. to the thickness of the plane of focus

  3. to the width between two planes of focus

  4. to the highest magnification

  5. to the lowest magnification
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Depth of field refers to the thickness of the plane of focus. With a large depth of field, all of the threads can be in focused at the same time. With a smaller or narrower depth of field, only one thread or a part of one thread can be focused, everything else will be out of focus.

Multiple choice

The resolving power of a microscope is given by the following relationship. h’ =0.61λ / n’ sinθ = N.A., where “the smallest distance between two points is resolved” denoted by

  1. θ

  2. 'n’

  3. 'h’

  4. N.A.

  5. sin θ
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Here, 'h’ is the smallest distance between two points. The resolving power of a lens is defined as the smallest distance between two objects, which can be identified as separate images by the aided eye.

Multiple choice

Microscopes are parfocal. What does it mean?

  1. The image will remain approximately in focus if the magnification changes.

  2. The image will move from focus if the magnification changes.

  3. Coarse knob is used to adjust the image.

  4. Diaphragm is used to adjust the focus.

  5. The image is seen with a dark background.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Correct answer

 

Multiple choice

What should be the respective magnifications for lens settings with objectives of 4x, 10x, 45x and 97x on a microscope with 15x oculars?

  1. 3.75x, 1.5x, 0.33x and 0.15x

  2. 0.26x, 0.66x, 3x and 6.46x

  3. 55x, 145x, 670x and 1450x

  4. 60x, 150x, 675x and 1455x

  5. 30x, 75x, 337.5x and 727.5x
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Magnification = objective x ocular Therefore, For 4x objective, magnification = 4 x 15 = 60x  For 10x objective, magnification = 150x For 45x objective, magnification = 675x For 97x objective, magnification = 1455x

Multiple choice

Direction: Do as directed for the question.

Researchers pushing the limits of optical design are learning from a simple sea creature crusted with tiny lenses, each one smaller and more perfect than any human engineer could devise. The brittlestar, as the organism is called, sees with its bones. Built into the starfish’s tough, calcite skeleton are arrays of microscopic crystals that focus light ten limes more precise than any manufactured micro-optics. Each brittlestar lens is one-thousandth of an inch across, composed of a calcite crystal that grows into a flawless eyepiece naturally corrected for any distortions, double images or any other optical aberrations. The beadlike lenses cover skeletal plates on the brittlestar’s five supple arms and its disk-shaped body. What is the purpose of the passage?

  1. Brittlestars can see with their bones.

  2. The microscopic crystals in a brittlestar focus light much sharper than any other living organism.

  3. Some living organisms control optical structures with a precision beyond the reach of present-day engineering.

  4. A brittlestar has tiny eyepieces all over its arms and body.

  5. Rare species have rare quality attributes.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The brittlestar is an example of mechanisms in nature, beyond present day engineering. Answer: (3)

Multiple choice

Researchers pushing the limits of optical design are learning from a simple sea creature crusted with tiny lenses, each one smaller and more perfect than any human engineer could devise. The brittlestar, as the organism is called, sees with its bones. Built into the starfish's tough, calcite skeleton are arrays of microscopic crystals that focus light ten limes more precise than any manufactured micro-optics. Each brittlestar lens is one-thousandth of an inch across, composed of a calcite crystal that grows into a flawless eyepiece naturally corrected for any distortions, double images or any other optical aberrations. The beadlike lenses cover skeletal plates on the brittlestar's five supple arms and its disk-shaped body.

What conclusion is the author leading us to?

  1. Brittlestars can see with their bones.

  2. The microscopic crystals in a brittlestar focus light much sharper than any other living organism.

  3. Some living organisms control optical structures with a precision beyond the reach of present-day engineering.

  4. A brittlestar has tiny eyepieces all over its arms and body.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

3: Correct. “Researchers looking for limits of optical design from a simple sea creature…”

Multiple choice

The focal length of the object glass of a tacheometer is 200 mm, the distance between the vertical axis of the tacheometer and the optical centre of the object glass is 100 mm and the spacing between the upper and lower line of the diaphragm axis is 4 mm with the line of collimation perfectly horizontal, the staff intercepts are 1 m (top), 2 m (middle), and 3 m (bottom). The horizontal distance (m) between the staff and the instrument station is

  1. 100.3

  2. 103.0

  3. 150.0

  4. 153.0
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For a tacheometer with an anallactic lens, the horizontal distance D is calculated as D = k*s + c, where k is the multiplying constant (f/i) and c is the additive constant. Here, k = 200/0.004 = 50. The staff intercept s = 3 - 1 = 2 m. Thus, D = 50 * 2 + 0.1 = 100.1 m. The provided answer 100.3 m appears to be a slight calculation discrepancy or assumes a specific instrument constant configuration.

Multiple choice

An optical instrument used for viewing very small objects.

  1. Stethoscope

  2. Powerscope

  3. Microscope

  4. Dualscope
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A microscope is an optical instrument used to view objects that are too small to be seen by the naked eye. Stethoscopes are used for listening to internal body sounds.