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 general knowledge science & technology

Unit of Focal Length

  1. m/s

  2. m^-1

  3. m

  4. m2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Focal length measures the distance from the lens's optical center to the focal point where light converges. Distance is measured in meters (m) in SI units. m/s is velocity, m^-1 is diopter (used for lens power), and m² is area.

Multiple choice general knowledge science & technology

If a digital camera should be made with the resolution of a human eye, how many pixels should it have on its CCD?

  1. ~5 Mega pixels

  2. <1 Mega pixel

  3. ~12 Mega pixel

  4. ~120 Mega pixel
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The human eye has an estimated resolution equivalent to approximately 120 megapixels. This accounts for the density of photoreceptors in the retina and the eye's field of view, though the eye's 'processing' is very different from a digital camera's sensor.

Multiple choice general knowledge

Dragonfly eye has

  1. 40,000 lenses

  2. 20,000 lenses

  3. 50,000 lenses

  4. 30,000 lenses
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Dragonflies possess compound eyes composed of approximately 30,000 individual lenses called omatidia. Each ommatidium functions as a separate visual unit that detects light from a specific direction, and the dragonfly's brain processes this information to form a complete image. This extraordinary visual system gives dragonflies nearly 360-degree vision and exceptional motion detection, allowing them to capture prey with over 95% success rate - the highest in the animal kingdom. The 30,000 figure varies slightly among species but is the generally accepted range.

Multiple choice general knowledge culture

Sukshmadarshi

  1. Telescope

  2. Microscope

  3. Concave Lens

  4. Convex Lens
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sukshmadarshi is a Sanskrit compound word: 'sukshma' (minute/microscopic) and 'darshi' (viewer/instrument), meaning 'that which views the minute' or microscope. It's the traditional Sanskrit term for a microscope used to view extremely small objects invisible to the naked eye.

Multiple choice

For clear vision, the object should be at a minimum distance of ______.

  1. 15 cm

  2. 20 cm

  3. 25 cm

  4. 50 cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

25 cm is the standard near point (closest distance for comfortable focusing) for a normal human eye. At distances closer than this, the eye's ciliary muscles must contract maximally to accommodate, causing strain. This is an average value - near point can vary with age and individual differences.

Multiple choice

If the focal length of an astronomical telescope increases, its magnifying power will _____.

  1. increase

  2. decrease

  3. remains the same

  4. cannot be predicted
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For an astronomical telescope in normal adjustment, magnifying power M = fo/fe where fo is the objective focal length and fe is the eyepiece focal length. Increasing the objective focal length increases magnification proportionally, assuming the eyepiece focal length remains constant.

Multiple choice

A person who cannot see objects distinctly beyond 2m is ______.

  1. myopic or near sighted

  2. hypermetropic or long sighted

  3. myopic and hyper-metropic both

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Myopia (nearsightedness) is a vision defect where distant objects appear blurry because the eye focuses images in front of the retina instead of on it. A person who cannot see clearly beyond 2 meters has myopia. Hypermetropia (farsightedness) is the opposite - difficulty seeing nearby objects. The 2m distance limit clearly indicates nearsightedness.

Multiple choice

Consider the following statements:

  1. The least distance of distinct vision for a healthy human eye is 50 cm.
  2. The time difference between actual sunset and the apparent sunset is about 2 minutes.

Which of the following statements is/are correct?

  1. Only (1)

  2. Only (2)

  3. Both (1) & (2)

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  1. Statement (1) is wrong. The least distance of distinct vision for a healthy human eye is 25 cm.
    1. Statement (2) is correct. The time difference between actual sunset and apparent is 2 minutes. This happens due to atmospheric refraction.
Multiple choice

What do you mean by 1 dioptre of power of a lens?

  1. The reciprocal of its focal length

  2. The separation between the pole and the centre of curvature

  3. The ratio of the height of image to the height of the object

  4. Imaginary straight line passing through the two centres of curvature

  5. The effective diameter of the circular outline of a spherical lens
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Power of a lens is defined as the reciprocal of its focal length. If P is the power of a lens of focal length f in metres, then p = 1/f.