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 botany cell and cellular organization cell theory microscope cell and its discovery

Stop disc is used in which microscope?

  1. Compound light microscope

  2. Differential interference contrast microscope

  3. Dark field microscope

  4. Phase contrast microscope
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A stop is an opaque object that blocks the central light when placed underneath the stage condenser. This also causes light to scatter in all azimuths, resulting in a cone of light that allows for dark field observation.

So C is correct option. 

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

What is the magnification of scanning probe microscope?

  1. 100-200x

  2. 200-500x

  3. 800–1000x

  4. 1500-2000x
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Scanning probe microscopes, such as the AFM or STM, are known for extremely high magnification capabilities, often reaching into the range of 1000x or significantly higher depending on the specific application and setup.

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

The types of lenses in a compound microscope are

  1. $3$.
  2. $4$.
  3. $2$.
  4. $1$.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
There are three main types of optical telescopes; refractive, reflective, and catadioptric. Refractive telescopes, such as the one invented by Galileo, use an objective lens and an eyepiece.
So the correct option is A. 
Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

In light microscope which lens does not take part in image formation?

  1. Objective$(5X)$
  2. Objective$(45X)$

  3. Condenser(D)

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

In a standard light microscope, the condenser is used to focus light onto the specimen, but it does not contribute to the magnification or the formation of the final image seen by the eye, unlike the objective and ocular lenses.

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

The resolving power of a compound microscope will enhance with

  1. Increase in both wavelength of light and numerical aperture.

  2. Decrease in both wavelenth of light and numerical aperture.

  3. Decrease in wavelength of light and increase in numerical aperture.

  4. Increase in wavelength of light and decrease in numerical aperture.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The resolving power of a compound microscope can be defined as the ability of the microscope to form separate images of two objects placed very close to each other.
The resolving power of the compound microscope will increase with a decrease in wavelength of light and an increase in the numerical aperture.
So, the correct answer is 'Decrease in wavelength of light and an increase in the numerical aperture'.
Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

A compound microscope has the widest field when eyepiece and objective lenses are .............. respectively.

  1. $10X, 5X$
  2. $15X, 5X$
  3. $5X, 5X$
  4. $5X, 45X$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The field of view in a microscope is inversely proportional to the magnification of the lenses. Using lower power lenses (10x eyepiece and 5x objective) results in the widest field of view compared to higher magnification combinations.

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

Light microscopes

  1. Work by reflecting electrons off the surface of an object being studied

  2. Can generally magnify objects about 10,000 times without blurring

  3. Use light and glass lenses to magnify an image

  4. Provides more resolution than an electron microscope
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The microscope is the instrument used to magnify the image of an object that we cannot see by our naked eyes. It is of two types on the basis of a number of lenses, simple microscope, and compound microscope. A light microscope is a compound microscope that uses focused light and two lenses to magnify a specimen.

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

If a microscope has a $10\times$ objective lens and $10\times$ ocular lens, it would magnify the object by 

  1. $10\times$
  2. $20\times$
  3. $50\times$
  4. $100\times$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The compound microscope is the instrument used to magnify the image of the object that we cannot see by naked eyes. It uses two lenses or lens systems, one is the objective lens which enlarged the image of the object and the second is an ocular lens which magnifies the image formed by the first. The total magnification is the product of the magnifications of two lens systems. Hence, the microscope which has a 10X objective lens and 10X ocular lens, it would magnify the object by 10 × 10 = 100 times. 

Multiple choice botany cell and cellular organization cell theory microscope cell and its discovery

The strength of magnification of oil immersion lens is

  1. $20\times$
  2. $500\times$
  3. $1000\times$
  4. $100\times$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
There are three types of objective lens: 10X (low power objective lens); 40X (high power objective lens) and 100X (oil immersion objective lens). Each objective lens is represented by a particular colour. Oil immersion is the technique used to increase the resolving power of the microscope. In this technique, oil is used to avoid the different refractive index of air and glass which affect the numerical aperture.
Multiple choice

Should you start on high power objective on a microscope? 

  1. yes

  2. no
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

You should always start focusing with the lowest power objective lens because it has a wider field of view, making it easier to locate the specimen. Starting on high power increases the risk of crashing the lens into the slide and makes focusing very difficult. Once the specimen is centered and focused, you can safely rotate to higher powers.

Multiple choice

What is the total magnification of a microscope if the eyepiece is 10x and the other is 40x? 

  1. 50x

  2. 400x

  3. 4000x

  4. 40x
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

To find the total magnification of a microscope, you multiply the magnification of the eyepiece by the magnification of the objective lens. Multiplying 10 by 40 gives a total magnification of 400x. Adding the magnifications together is a common mistake that leads to the incorrect answer of 50x.

Multiple choice

With a telescope, you can see

  1. the same mumber of stars you can see with just your eyes.

  2. more stars than than you can see with just your eyes.

  3. fewer stars than you can see with just your eyes
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Telescopes gather light from objects that are too faint or too far away for the naked eye to detect. This allows observers to see many more stars than are visible without assistance.