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

what effect can a lens in the eye have on the lasers energy

  1. partially block it

  2. magnify its intensity by as much as 100,000

  3. magnify its intensity by as much as 100

  4. completely block it
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The lens of the human eye acts as a natural magnifier. If a laser beam enters the eye, the lens can focus that energy onto the retina, magnifying its intensity by up to 100,000 times, which causes severe and permanent damage.

Multiple choice digital painting tux paint physics

What is the maximum size to which you magnify the picture?

  1. $2x$
  2. $4x$
  3. $6x$
  4. $8x$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Maximum size to which you magnify the picture is 8x.

Minimum size to which you magnify the picture is 2x
Magnify the picture is the process of enlarging the apparent size like zoom in the picture.

Multiple choice physics motion and measurement measuring length measurement of small and large distances measurement of distance

Which of the following is the best method to measure microscopic distances?

  1. Optical microscope

  2. Meter scale

  3. Screw gauge

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

Optical microscopes are enabled with objective fitted with lenses with different magnifications. This helps to magnify a small objects and so necessary measurements.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

A reflecting telescope has a large mirror for its objective with radius of curvature equal to 80 cm. The magnifying power of this telescope if eye piece used has a focal length of 1.6 cm is:

  1. 100

  2. 50

  3. 25

  4. 5
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The focal length of objective mirror $f _0 = \dfrac{R}{2} = \dfrac{80}{2} = 40 \,cm$
and focal length of eye piece = 1.6 cm
$\therefore $ magnifying power, $m = \dfrac{f _0}{f _e} = \dfrac{40}{1.6 } = 25$

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

A telescope is used to resolve two stars separated by $4.6 \, \times \, 10^{-6}$ rad. If the wavelength of light used is 5460 $\overset{0}{A}$, what should be the aperture of the objective of the telescope? 

  1. 0.1488 m

  2. 0.567 m

  3. 1 m

  4. 2 m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Aperature of the telescope, $D = \dfrac{1.22\lambda}{d\theta}$ 


Here, $\lambda = 5460\ \overset{0}{A} = 5460 \times 10^{-10}m$


$ d\theta= 4.6 \times10^{-6}\ rad$

$\therefore D = \dfrac{1.22\times5460\times10^{-10}}{4.6\times 10^{-6}}$
$ = 0.1488m $

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

In an astronomical telescope of refracting type:

  1. Eyepiece has greater focal length

  2. Objective has greater focal length

  3. Objective and eyepiece have equal focal length

  4. Eyepiece has greater aperture than the objective
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An astronomical telescope of refracting type has objective of greater focal length to have more surface area for incoming light from celestial bodies. 

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

Four lenses of focal length $+15cm,+20cm,+150cm$ and $+250cm$ are available for making an astronomical telescope. To produce the largest magnification, the focal length of the eyepiece should be

  1. $+15cm$
  2. $+20cm$
  3. $+150cm$
  4. $+250cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In astronomical telescope, magnification is inversely proportional to focal length of eye piece. Hence, it will be minimum i.e. +15cm as in question.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

For an electron microscope, which of the following is false ?

  1. It uses magnetic lens to converge electron beam.

  2. Its resolving power is directly proportional to accelerating potential of electron.

  3. Its resolving power is inversely proportional to wavelength of electrons
  4. Magnification attained with the help of of it of the order of $10^6$.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For an electron microscope: (A) is correct - magnetic lenses are used to focus the electron beam. (C) is correct - resolving power is inversely proportional to electron wavelength (R ∝ 1/λ). (D) is correct - electron microscopes can achieve magnifications of ~10⁶. (B) is FALSE - resolving power is NOT directly proportional to accelerating potential; it increases with potential because higher potential reduces electron wavelength (λ = h/√(2meV)), but this is an inverse relationship, not direct proportionality.