Tag: option c: imaging

Questions Related to option c: imaging

A prism of a certain angle deviates the red and blue rays by $8$ and $12$ respectively. Another prism of the same angle deviates the red and blue rays by $10$ and $14$ respectively. The prisms are small angled and made of different materials. The dispersive powers of the materials of the prisms are in the ratio

perceive colours resolution of optical instruments lenses option c: imaging physics

  1. $11 : 9$

  2. $6 : 5$

  3. $9 : 11$

  4. $5 : 6$

Show answer
Correct Option: B
Explanation:
Dispersive power $= \cfrac{\mu _v - \mu _r}{\mu _y -1} = \cfrac{\delta _v + \delta _r}{\delta _y}$

$\delta _y = \cfrac{\delta _v + \delta _r}{2}$

The ratio of dispersive power is;
$\cfrac{12-8}{\cfrac{12+8}{2}}$= $\cfrac{\cfrac{4}{10}}{\cfrac{4}{12}}$ =$ \cfrac{12}{10} $= $ 6 : 5 $

When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is.

perceive colours resolution of optical instruments lenses option c: imaging physics

  1. Polarised

  2. Of longer wavelength largest

  3. Of shorter wavelength

  4. Of high intensity

Show answer
Correct Option: C
Explanation:

The resolving power of an instrument depends upon the wave length of light used. The lower the wavelength of light higher is the accuracy in vision.
$\left(Resolving\, power \,\alpha \frac{1}{\lambda}\right)$

Calculate the dispersive power for glass from the given data $\mu _v=1.523$, and $\mu _r=1.5145$.

perceive colours resolution of optical instruments lenses option c: imaging physics

  1. 0.0012

  2. 0.2333

  3. 0.1639

  4. 0.9

Show answer
Correct Option: C
Explanation:

Mean refractive index   $\mu = \dfrac{\mu _v+\mu _r}{2} = \dfrac{1.523+1.5145}{2} = 1.5192$

Dispersive power   $w = \dfrac{\mu _v - \mu _r}{\mu -1}$
$\implies \ w = \dfrac{1.523 - 1.5145}{1.5192 -1} = 0.01637$

If the refractive indices of a prism for red, yellow and violet colours be 1.61, 1.63 and 1.65 respectively, then the dispersive power of the prism will be:

perceive colours resolution of optical instruments lenses option c: imaging physics

  1. $\dfrac { 1.65-1.62 }{ 1.61-1 }$

  2. $\dfrac { 1.62-1.61 }{ 1.65-1 }$

  3. $\dfrac { 1.65-1.61 }{ 1.63-1 }$

  4. $\dfrac { 1.65-1.63 }{ 1.61-1 }$

Show answer
Correct Option: C
Explanation:

Dispersive power of the prism=$\dfrac{\mu _v-\mu _r}{\mu _y-1}=\dfrac{1.65-1.61}{1.63-1}$

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:

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

  1. 100

  2. 50

  3. 25

  4. 5

Show answer
Correct Option: C
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, $m = \dfrac{f _0}{f _e} = \dfrac{40}{1.6 } = 25$

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? 

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

  1. 0.1488 m

  2. 0.567 m

  3. 1 m

  4. 2 m

Show answer
Correct Option: A
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 $

If you want to make Refracting Telescope, what components will you choose ?

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

  1. One convex led and one concave lens.

  2. Two convex lenses.

  3. One concave mirror, one plane mirror and one convex lens.

  4. Once concave mirror, one convex mirror and one convex lens.

Show answer
Correct Option: B
Which material should be chosen to make the concave mirrors of a high resolution telescope so that it can also withstand temperature variations?
physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

  1. Quartz

  2. Flint glass

  3. Crown glass

  4. Combination of Flint and Silica

Show answer
Correct Option: A
Explanation:

Quartz makes an ideal mirror. Its high hardness results in the smoothest micropolished surface possible, and its thermal dimensional stability allows the optician to produce a flat surface with almost no edge defects.

Scientists identify the elements that are burning in the stars by using which of the following devices?

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

  1. Refractive telescopes

  2. Reflective telescopes

  3. Spectroscopes

  4. Polarimeters

  5. Photoelectric mircoscopes

Show answer
Correct Option: C
Explanation:
Using the spectroscope, scientists can separate the individual line spectra of the elements that are burning in the stars and therefore identify the elements.

Two convex lenses of focal length 0.3 m and 0.05 m are used to make a telescope. The distance kept between them is equal to 

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

  1. 0.35 m

  2. 0.25 m

  3. 0.175 m

  4. 0.15 m

Show answer
Correct Option: A
Explanation:

To make a Telescope,
$L= f _{0}+f _{e}$

$= 0.3+0.05$

$= 0.35m$