CBSE Questions for Class 12 Medical Physics Wave Optics Quiz 14 - MCQExams.com

When an object is viewed with a light of wavelength $$6000\mathring{A}$$ under a microscope, its resolving power is $$10^4$$. The resolving power of the microscope when the same object is viewed with a light of wavelength $$4000\mathring{A}$$, is:
  • $$1.5 \times 10^4$$
  • $$2\times 10^4$$
  • $$3\sqrt{2}\times 10^4$$
  • $$3\times 10^4$$
  • $$ 10^4$$
Let a beam of wavelength $$\lambda$$ fall on parallel reflecting planes with separation $$d$$, then the angle $$\theta$$ that the beam should make with the planes so that reflected beams from successive planes may interfere constructive should be (where, $$n = 1, 2, ....)$$.
679208_3b8fe85753f34c8a88044913af5bb327.png
  • $$\cos^{-1}\left (\dfrac {n\lambda}{2d}\right )$$
  • $$\sin^{-1}\left (\dfrac {n\lambda}{2d}\right )$$
  • $$\sin^{-1}\left (\dfrac {n\lambda}{d}\right )$$
  • $$\tan^{-1}\left (\dfrac {n\lambda}{d}\right )$$
In Young's double slit experiment, one of the slit is wider than another, so that amplitude of the light from one slit is double of that from other slit. If $$I_m$$ be the maximum intensity, the resultant intensity I when they interfere at phase difference $$\phi$$ is given by.
  • $$\displaystyle\frac{I_m}{9}(4+5\cos\phi)$$
  • $$\displaystyle\frac{I_m}{3}\left(\displaystyle 1+2\cos^2\frac{\phi}{2}\right)$$
  • $$\displaystyle\frac{I_m}{5}\left(\displaystyle 1+4\cos^2\frac{\phi}{2}\right)$$
  • $$\displaystyle\frac{I_m}{9}\left(\displaystyle 1+8\cos^2\frac{\phi}{2}\right)$$
The phases of the light wave at c, d, e and f are $$\phi_c, \phi_d, \phi_e$$ and $$\phi_f$$ respectively. It is given that $$\phi_c \neq \phi_r$$
524731_eda1b927f9cc4e2a8cfa562e791f08a6.JPG
  • $$\phi_c$$ cannot be equal to $$\phi_d$$
  • $$\phi_d$$ cannot equal to $$\phi_e$$
  • $$(\phi_d - \phi_f)$$ is equal to $$(\phi_c - \phi_e)$$
  • $$(\phi_d - \phi_c)$$ is not equal to $$(\phi_f - \phi_e)$$
A vessel $$ABCD$$ of $$10\ cm$$ width has two small slits $$S_{1}$$ and $$S_{2}$$ sealed with identical glass plates of equal thickness. The distance between the slits is $$0.8\ mm$$. $$POQ$$ is the line perpendicular to the plane $$AB$$ and passing through $$O$$, the middle point of $$S_{1}$$ and $$S_{2}$$. A monochromatic light source is kept at $$S, 40\ cm$$ below $$P$$ and $$2m$$ from the vessel, to illuminate the slits as shown in the figure below. Calculate the position of the central bright fringe on the other wall $$CD$$ with respect to the line $$OQ$$. Now, a liquid is poured into the vessel and filled up to $$OQ$$. The central bright fringe is found to be at $$Q$$. Calculate the refractive index of the liquid.
1010807_285adbadd74043da834059990bd7df37.png
  • (a) $$y = 2\ cm$$. (b) $$\mu = 1.0016$$.
  • (a) $$y = 2\ cm$$. (b) $$\mu = 2.0016$$.
  • (a) $$y = 12\ cm$$. (b) $$\mu = 1.0016$$.
  • (a) $$y = 2\ cm$$. (b) $$\mu = 13.0016$$.
Two cohorent monochromatic light beams of intensities 4I and 9I interfere in a Young's double slit experimental setup to produce a fringe pattern on the screen. The phase difference between the beams at two points P and Q on the screen are $$\pi/2$$ and $$\pi/3$$ respectively. Then the ratio of the two intensities $$I_P/I_Q$$ is
  • 0
  • $$\displaystyle \frac{6}{19}$$
  • $$\displaystyle \frac{13}{19}$$
  • $$\displaystyle \frac{6}{13}$$
Two coherent poiunt sources of frequency $$(f=\dfrac {10v}{d}$$ where $$v$$ is speed of light) are placed at a distance $$d$$ apart as shown in figure. The receiver is free to move along the dotted line shown in the figure. Find the total number of maxima observed by the receiver.
877202_8d24f4a73b064ed680e0f65435500850.png
  • $$6$$
  • $$7$$
  • $$5$$
  • $$8$$
In the adjacent, $$CP$$ represents a wavefront and $$AO$$ & $$BP$$, the corresponding two rays. Find the condition on $$\theta$$ for constructive interference at $$P$$ between the ray $$BP$$ and reflected ray $$OP$$.
1014832_6ba7b8f1dc554663bd09a26e03ec6989.png
  • $$\cos { \theta } =3\lambda /2d$$
  • $$\cos { \theta } =\lambda /4d$$
  • $$\sec { \theta } -\cos { \theta } =\lambda d$$
  • $$\sec { \theta } -\cos { \theta } =4\lambda d$$
In a Youngs double-slit experiment, let $$\beta$$ be the fringe width, and let $${l}_{0}$$ be the intensity at the central bright fringe. At a distance $$x$$ from the central bright fringe, the intensity will be:
  • $${ l }_{ 0 }\cos { \left( \dfrac { x }{ \beta } \right) }$$
  • $${ l }_{ 0 }\cos ^{ 2 }{ \left( \dfrac { x }{ \beta } \right) }$$
  • $${ l }_{ 0 }\cos ^{ 2 }{ \left( \dfrac { \pi x }{ \beta } \right) }$$
  • $$\dfrac { { l }_{ 0 } }{ 4 } \cos ^{ 2 }{ \left( \dfrac { \pi x }{ \beta } \right) }$$
In Youngs double slit experiment, the fringes are displaced by a distance $$x$$ when a glass plate of one refractive index $$1.5$$ is introduced in the path of one of the beams. When this plate in replaced by another plate of the same thickness, the shift of fringes is $$(3/2)x$$. The refractive index of the second plate is
  • $$1.75$$
  • $$1. 50$$
  • $$1.25$$
  • $$1.00$$
In Youngs double slit experiment, the slits are $$2mm$$ apart and are illuminated with a mixture of two wavelengths $$\lambda=12000\ {A}^{o}$$ and $$\lambda=10000\ {A}^{o}$$. At what minimum distance from the common central bright fringe on a screen $$2m$$ from the slits will a bright fringe from one interference coincide with a bright fringe from the other?
  • $$3.2\ mm$$
  • $$6.0\ mm$$
  • $$7.2\ mm$$
  • $$9.2\ mm$$
Consider a two slit interference arrangements such that the distance of the screen from the slits is half the distance between the slits. Obtain the value of D in terms of $$\lambda$$ such that the first minima on the screen falls at a distance D from the centre O.
944172_a6f39dd0526d42e488f87736c8bae093.png
  • $$\dfrac{\lambda}{2.472}$$
  • $$\dfrac{\lambda}{2.236}$$
  • $$\dfrac{\lambda}{1.227}$$
  • $$\dfrac{\lambda}{3.412}$$
A point source of monochromatic light is situated at the centre of a circle, what is the phase difference between the light waves passing through the end points of any diameter
  • $$\dfrac{\pi}{2}$$
  • $$\pi$$
  • $$\dfrac{3\pi}{2}$$
  • $$zero$$
In a YDSE with two identical slits, when the upper slit is covered with a thin, perfectly transparent sheet of mica, the intensity at the centre of screen reduces from its initial value. Second order minima is observed to be above this point and second order maxima below it. Which of the following can not be a possible value of phase difference caused by the mica sheet?
  • $$\dfrac{\pi }{3}$$
  • $$\dfrac{{7\pi }}{2}$$
  • $$\dfrac{{10\pi }}{3}$$
  • $$\dfrac{{11\pi }}{3}$$
In the figure shown if a particle beam of white light is incident on the plane of the slits then the distance of the white spot on the screen from$$O$$ is [Assume $$d <  < D,\lambda  <  < d$$ ]
1130227_f88e30ca49414d82a43c5edee97698e2.PNG
  • $$0$$
  • $$d/2$$
  • $$d/3$$
  • $$d/6$$
A slit $$5.0cm$$ wide is irradiated normally with microwaves of wavelgnth $$1.0cm$$. Then the angular spread of the central maximum on either side of the incident light is nearly:
  • $$(1/5)$$ radian
  • $$4$$ radisn
  • $$5$$ radian
  • $$6$$ radian
In Young's double slit experiment, the slits are $$2$$ mm apart and are illuminated by photons of two wavelengths $$\lambda_1=12000\overset{o}{A}$$ and $$\lambda_2=10000\overset{o}{A}$$. At what minimum distance from the common central bright fringe on the screen $$2$$ m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other?
  • $$3$$ mm
  • $$8$$ mm
  • $$6$$ mm
  • $$4$$ mm
Initially interference is observed with the entire experimental set up inside a chamber filled with air, Now  the chamber is evacuated. With the same source of light used, a careful observer will find that.
  • The interference pattern is almost absent as it is very much diffused
  • There is no change in the interference pattern
  • The fringe width is slightly decreased
  • The fringe width is slightly increased
In Young's double slit experiment shown in figure. $${S}_{1}$$ and $${S}_{2}$$ are coherent souces and $$S$$ is the screen having a hole at a point $$1.0mm$$ away from the central line. White light  ($$400$$ to $$700nm$$) is sent through the slits. Which wavelengths passing through the hole has strong intensity? 
1265722_d0ed371096cb4e88a4b3b7cca5b322ec.png
  • $$400nm$$
  • $$700nm$$
  • $$500nm$$
  • $$667nm$$
A glass plate of refractive index, $$1.5$$ is coated with a thin layer of thickness t and refractive index $$1.8$$. Light of wavelength $$648$$ nm travelling in air is incident normally on the layer. It is partly reflected at upper and lower surfaces of the layer and the rays interfere constructively is?
  • $$30$$ nm
  • $$60$$ nm
  • $$90$$ nm
  • $$120$$ nm
In single slit Fraunhoffer diffraction which type of wave front is required : 
  • cylindrical
  • spherical
  • elliptical
  • plane
A beam of $$2000$$ eV electrons are incident normally on the surface of crystal whose inter atomic separation is $$0.11 $$ nm. The mass of the electron can be takes as $$9\times 10^{-31}$$ kg. At what angle to the normal can we observe a diffraction maxima.
  • $$ sin ^{-1}\left(\dfrac{1}{4}\right)$$
  • $$ cos ^{-1}\left(\dfrac{1}{4}\right)$$
  • $$ sin ^{-1}\left(\dfrac{1}{2}\right)$$
  • $$ cos ^{-1}\left(\dfrac{1}{2}\right)$$
A thin slice is cut of glass cylinder along a plane parallel to its axis. The slice is placed on a flat glass plate with the curved sirface sownwards. Monochromatic light is incident normally from the top. the observed interfernce fringes from the combination do not follow on of the following staements. 
  • The frings are straight and parallel to the length of the pleace.
  • The line of contract of the cylindrical glass piece and the glass plate appears dark.
  • The fring spacing increases as we go outwards
  • The frings are fomed due to the interference of light rays reflected from the curved surface of the cylindrical place and the top surfce of the glass plate.
Interference fringes were produced in Young's double slit experiment using light of wavelength $$5000\overset{o}{A}$$. When a film of thickness $$2.5\times 10^{-3}$$cm was placed in front of one of the slits, the fringe pattern shifted by a distance equal to $$20$$ fringe-widths. The refractive index of the material of the film is?
  • $$1.25$$
  • $$1.35$$
  • $$1.4$$
  • $$1.5$$
In a double slit experiment, sodium light of wavelength 589 nm produces fringes spaced 1.8 mm on a screen. If the source is replaced by another one of wavelength 436 nm the fringe spacing is :
  • 1.33 mm
  • 2.3 mm
  • 0.33 mm
  • 2 mm
Two slits in Young's double-slit experiment have widths in the ratio 9 : 4.Find the ratio of light intensities at maxima and minima in the interference pattern:
  • 25:16
  • 25:1
  • 5:1
  • 5:16
In case of diffraction pattern of a single slit under polychromatic illumination first minima of wavelength $${ \lambda  }_{ 1 }$$ is found coincide with the second maximam of wavelength $${ \lambda  }_{ 2 }$$ then
  • $$3{ \lambda }_{ 1 }=2{ \lambda }_{ 2 }$$
  • $$2.5{ \lambda }_{ 1 }={ \lambda }_{ 2 }$$
  • $${ \lambda }_{ 1 }={ 3.5\lambda }_{ 2 }$$
  • $$5{ \lambda }_{ 1 }={ \lambda }_{ 2 }$$
The beams, $$A$$ and $$B$$ of plane polarized light with mutually perpendicular planes of polarization are seen through a polaroid. From the position when the beam. A has maximum intensity (and beam $$B$$ has zero intensity), a rotation of polaroid through $$30^{\circ}$$ makes the two beams appear equally bright. If the initial intensities of the two beams are $$I_{A}$$ and $$I_{B}$$ respectively, then $$\dfrac {I_{A}}{I_{B}}$$ equals.
  • $$3$$
  • $$\dfrac{3}{2}$$
  • $$1$$
  • $$\dfrac{1}{3}$$
The path difference between two identical waves arriving at a point is $$120\lambda $$, if the path difference is $$72\mu m$$ then:
  • wavelength of light is $$6000 A$$ and the point is bright
  • wavelength of light is $$6000\,{A^ \circ }$$ and the point is dark
  • wavelength of light is $$5000 A$$ and the point is bright
  • wavelength of light is $$5000 A$$ and the point is dark
In young's double slit experiment, D=1.5 m, $$ d=4.5 \times 10^{-3} $$ m and fringe width x=0.2 mm. what is the path difference between the interfering beams for two successive maxima ?
  • $$ 4.5 \times 10^{-7} $$
  • $$ 5.25 \times 10^{-7} $$
  • $$ 6 \times 10^{-7} $$
  • $$ 2\times 10^{-7} $$
In a double slit experiment, the two slits are $$1\ mm$$ apart and the screen is placed $$1\ m$$ away. A monochromatic light wavelength $$500\ nm$$ is used. What will be the width of each slit for obtaining ten maxima of double slit with in the central maxima of single slit pattern ?
  • $$0.1\ mm$$
  • $$0.5\ mm$$
  • $$0.02\ m$$
  • $$0.2\ mm$$
$$Statement-1:$$ On viewing the clear blue portion of the sky through a Calcite Crystal, the intensity of transmitted light varies as the crystal is rotated.
$$Statement-2:$$ The light coming from the sky is polarized due to scattering of sun light by particles in the atmosphere. The scattering is largest for blue light.
  • State-1 is false, statement-2 is true
  • State-1 is true, statement-2 is false
  • State-1 is true, statement-2 true, statement-2 is the correct explanation of statement-1
  • State-1 is true, statement-2 true, statement-2 is not correct explanation of statement-1
A double slit apparatus is immersed in a liquid of refractive index $$\mu_m$$. It has a slit separation $$d$$ and the distance between the plane of the slits and the screen as $$D(D > > d)$$. The slits are illuminated by a parallel beam of wavelength $$\lambda_{0}$$. The smallest thickness of a sheet of refractive index $$\mu_{p}$$ to bring adjacent minima on the axis is
  • $$\dfrac {\lambda_{0}}{2(\mu_{p} - \mu_{m})}$$
  • $$\dfrac {(\mu_{p} - \mu_{m})\lambda_{0}}{2}$$
  • $$\dfrac {\lambda_{0}}{(\mu_{p} - \mu_{m})}$$
  • $$(\mu_{p} - \mu_{m})\lambda_{0}$$
Two sources $$S_{1}$$ and $$S_{2}$$ of intensity $$I_{1}$$ and $$I_{2}$$ are placed in front of a screen. [Fig.(a)] The pattern of intensity distribution seen in the central portion is given by Fig(b).
In this case, which of the following statements are true?
1369617_d91928cd6f914f1488a7b5a8f4bdd4f3.png
  • $$S_{1}$$ and $$S_{2}$$ have the same intensities
  • $$S_{1}$$ and $$S_{2}$$ have a constant phase difference
  • $$S_{1}$$ and $$S_{2}$$ have the same phase
  • $$S_{1}$$ and $$S_{2}$$ have the same wavelength
A beam of light consisting of two wavelength $$650\ nm$$ and $$520\ nm$$ is used to illuminate the slit of a Young's double slit experiment. Then the order of the bright figure of the longer wavelength that coincide with a bright fringe of the shorter wavelength at the least distance from the central maximum is:-
  • $$1$$
  • $$2$$
  • $$3$$
  • $$4$$
Direction of the second maximum in the Fraunhofer diffraction pattern at a single slit is given by (a is the width of the slit) :-
  • $$\operatorname { a \sin } \theta = \frac { \lambda } { 2 }$$
  • $$\operatorname { a \cos } \theta = \frac { \lambda } { 2 }$$
  • $$\operatorname { asin } \theta = \lambda$$
  • $$\operatorname { a \sin } \theta = \frac {3 \lambda } { 2 }$$
The intensity of the central fringes obtained in the interference pattern due to two identical slit source is $$I$$. When one of the slits is closed then the intensity at the same points is $$I_{0}$$. Then the correct relation ship between $$I$$ and $$I_{0}$$ is
  • $$I=I_{0}$$
  • $$I=2I_{0}$$
  • $$I=4I_{0}$$
  • $$I=I_{0}/4$$
In Young's double-slit experiment, the phase difference between the two waves reaching the location of the third dark fringe is
  • $$\pi$$
  • $$\dfrac {3\pi}{2}$$
  • $$5\pi$$
  • $$3\pi$$
$$\ln Y D S E , d = 2 \mathrm { mm } , D = 2 \mathrm { m }$$ and $$\lambda = 500 \mathrm { nm }$$ . If intensity of two slits are $$l _ { 0 }$$ and 9$$/ _ { 0 }$$ , then find intensity at $$y = \frac { 1 } { 6 } m m$$
  • $$7 I _ { 0 }$$
  • $$10 I _ { 0 }$$
  • $$16 I _ { 0 }$$
  • $$4 I _ { 0 }$$
An interference is observed due to two coherent sources 'A'  & 'B' separated by a distance of 4$$\lambda$$ along the y-axis where $$\lambda$$ is the wavelength of the source. A detector D  is moved on the positive x-axis. The number of points on the x-axis excluding the points, x =0 & x =$$\infty$$  at which maximum will be observed is..--
  • three
  • four
  • two
  • infinite
In a young's double slit experiment, d = 1 mm, $$\lambda$$ = 6000 A and D = 1 m (where d, $$\lambda$$ and D have usal meaning). Each of slit individually produces same intensity on the screen. The minimum distance between two points on the screen having 75% intensity of the maximum intensity is: 
  • 0.45 mm
  • 0.40 mm
  • 0.30 mm
  • 0.20 mm
An aperture of diameter 1.2 mm has been illuminated by monochromatic light. The diffracted light is observed on a screen. When the screen is gradually displaced towards the aperture, the centre becomes dark for the first time at a distance of 30cm from the aperture. The wavelength of light used is :
  • 6000$${A^ \circ }$$
  • 4000$${A^ \circ }$$
  • 8000$${A^ \circ }$$
  • 3000$${A^ \circ }$$
The near point of a long-sighted person is $$50\ cm$$ from the eye. Where can she see an object clearly:
  • A distance of $$20\ cm$$
  • Infinity
  • Both $$A$$ and $$B$$
  • None of these
Visible light passing through a circular hole from a diffraction disc of radius 0.1 mm on a screen. If X-ray is passed through the same set-up, the radius of the diffraction disc will be : 
  • zero
  • < 0.1 mm
  • 0.1 mm
  • > 0.1 mm

At the first  minimum adjacent to the central maximum of a single - slit diffraction pattern, the phase difference between the Huygen's wavelet form the edge of the slit and the wavelet from the midpoint of the slit is:
  • $$\dfrac{\pi }{8}radian$$
  • $$\dfrac{\pi }{4}radian$$
  • $$\dfrac{\pi }{2}radian$$
  • $$\pi \;radian$$
The double slit experiment of young has been shown in the figure: Q is the position of the first bright fringe on the right side and P is the $$11^{th}$$ fringe on the other side as measured from Q. If wavelength of light used is $$6000\overset { \circ  }{ A } $$ $$,{ S }_{ 1 }B$$ will be equal to:
1507572_daf2c6e2ee1a4dee8fa5fe0c2cf9390c.png
  • $$6\times10^{-6}m$$
  • $$6.6\times10^{-6}m$$
  • $$3.138\times10^{-7}m$$
  • $$3.144\times10^{-7}m$$
In a Young's double slit experiment the intensity at a point where the path difference is $$\lambda /6 (\lambda $$ being the wavelength of light used) is i. If $$I+o$$ denotes the maximum intensity, $$I/I_o$$ is equal to
  • $$3/4$$
  • $$1/\sqrt 2$$
  • $$\sqrt 3/2$$
  • $$1/2$$
An unpolarised light of intensity $$32  \mathrm{W} / \mathrm{m}^{2}  $$ passes through three polarisers, such that the transmission axis of last polarizer is perpendicular with the first. If the intensity of emergent light is $$3  \mathrm{Wh}  $$ Im $$ ^{2} $$ then the angle between the transmission axes of the first two polarisers is:
  • $$ 30^{\circ} $$
  • $$ 19^{\circ} $$
  • $$ 45^{\circ} $$
  • $$ 90^{\circ} $$
The distance between the two slits in a Young's double slit experiment is $$d$$ and the distance of the screen from the plane of the slits is $$b$$. P is a point on the screen directly in front of one of the slits. The path difference between the waves arriving at P from the two slits is 
  • $$\dfrac{d^2}{b}$$
  • $$\dfrac{d^2}{2b}$$
  • $$\dfrac{2d^2}{b}$$
  • $$\dfrac{d^2}{4b}$$
Consider the shown arrangement to obtain diffraction pattern when a monochromatic radiation of wavelength $$\lambda$$ is incident on the narrow aperture. If $$a = 3\lambda$$, in the diffraction pattern obtained on screen, the number of intensity minima would be
1704911_2b0d4dc47a0d4252bad5b283641fa6e8.png
  • $$3$$
  • $$4$$
  • $$5$$
  • $$6$$
0:0:1


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