CBSE Questions for Class 12 Medical Physics Wave Optics Quiz 11 - MCQExams.com

In the diffraction pattern due to a single slit of width 'd' with incident light of wavelength $$'\lambda '\quad $$, at an angle of diffraction $$'\theta '$$, the condition for first minimum is 
  • $$\lambda \quad sin\quad \theta \quad =\quad d$$
  • $$d\quad cos\quad \theta \quad =\quad \lambda $$
  • $$d\quad sin\quad \theta \quad =\quad \lambda $$
  • $$\lambda \quad cos\quad \theta \quad =\quad d$$
A source S is kept directly behind the slit $$S$$ , in a double-slit apparatus. Find the phase difference at a point $$O$$which is equidistant from $$s 1 8$$ s2 What will be the phase difference at $$\mathrm { P }$$ if a liquid of refraction index $$\mu$$ is filled. (wavelength of light in air is $$/$$ due to the source)$$( \lambda  < < d , d < < D , \langle > > d )$$
1379857_c88b07dc70c44922b0826bd4cba780d8.png
  • between the screen and the slits.
  • between the slits & the source S. In this case find the minimum distance between the points on the screen where the intensity is half the maximum
    intensity on the screen.
  • Beyond the slits.
  • None of these
Select the incorrect statement
  • The frequency of a wave depends on its source and not on the medium
  • Only a transverse wave can be polarised
  • For the propagation of mechanical wave the medium must be least elastic
  • The mechanical waves are always longitudinal as liquids and gases cannot sustain shear
Red light is generally used to observe diffraction pattern from single slit. If green light is used instead of red light then diffraction pattern :
  • Will be more clear
  • Will be contract
  • Will be expanded
  • Will not visualize
Ratio of width of principal maxima to the second order maxima in Fraunhofer single slit diffraction is
  • 4
  • 3
  • 2
  • 1
Coherent sources can be obtained:
  • only by division of wave front
  • only by division of amplitude
  • both by division of amplitude and wave front
  • none of the above
Which one of the following phenomena is not explained by Huygens construction of wave front ?
  • $$Refraction$$
  • $$Reflection$$
  • $$Diffraction$$
  • $$Origin$$ $$of$$ $$spectra$$
In YDSE, the spacing between the slits is d and wavelength of light used is 6000 A. If the angular width of a fringle formed on a distant screen is $$1^o$$, then value of d is
  • 1 mm
  • 0.05 mm
  • 0.03 mm
  • 0.01 mm
In a young double slit experiment, 12 fringe are observed to be formed in a certain segment of the screen when light of wavelength 600 m is used. If the wavelength of light is changed to 400 nm, number of fringes observed in the same segment of the screen is given by 
  • 12
  • 18
  • 24
  • 30
While moving from deep water to shallow water.
  • Frequency of the water waves decrease
  • Frequency of the water waves increase
  • Frequency of the water waves stays the same
  • None of the above
In a YDSE both slits produce equal intensities on the screen. A 100% transparent thin film is placed in front of one of the slits. Now the intensity of the geometrical centre of system on the screen becomes 75% of the previous intensity. The wavelength of the light is 6000A and $${ \mu  }_{ glass }=1.5.$$ The thickness of the film cannot be : 
  • 0.2 $${ \mu }m$$
  • 1.0 $${ \mu }m$$
  • 1.4 $${ \mu }m$$
  • 1.6 $${ \mu }m$$

Angle of polarization depends on 
  • incident angle
  • angle of refraction
  • type of medium
  • the angle of reflection.
Particle nature and wave nature of electomagnetic waves can be shown by
  • electron has small mass, deflected by the metal sheet
  • X-ray is diffracted a, reflected by thick metal sheet
  • light is refracted and diffracted
  • light is polarised and shows photoelectric effect.
The wavefronts of a light wave travelling in vacuum are given by x +y + z = c . the angle made by the direction of propogation of light with the X-axis is 
  • $$ 0^0 $$
  • $$ 45^0 $$
  • $$ 90^0 $$
  • $$ cos^{-1} ( 1/ V3 ) $$
Which of the following ray gives more distinct diffraction:
  • X-ray
  • light ray
  • y-ray
  • Radio wave
A diffraction grafting experiment is set up using orange light of wavelength $$600$$nm. The grating has a slit separation of $$2.00\mu m$$.
What is the angular separation $$(\theta_2-\theta_1)$$ between the first and second order maxima of the orange light?

1641905_9fa5a6b896874e86b85fa12d0d69f72e.png
  • $$17.5^o$$
  • $$19.4^o$$
  • $$36.9^o$$
  • $$54.3^o$$
Diffraction is a term used to describe one aspect of wave behaviour.
What does diffraction make possible?
  • The ability to hear around corners
  • The ability to hear high frequency and low frequency sound waves
  • The ability to hear loud and quiet sounds
  • The ability to hear sound through a brick wall
A pattern of waves was observed without being able to view the source of the waves. The pattern is represented in the diagram.
What can cause this pattern?

1648430_385eb3070a46488d9dbc4912a9bdbbc5.png
  • coherence only
  • diffraction and interference
  • diffraction only
  • interference only
A light has amplitude $$A$$ (after polariser) and angle between analyser and polariser is $$60^{\circ}$$. Light is reflected by analyser has amplitude
  • $$A\sqrt{2}$$
  • $$A/ \sqrt{2}$$
  • $$\sqrt{3} A/2$$
  • $$A /2$$
Which statement gives a condition that enables diffraction to occur?
  • A source of waves moves towards a stationary observer.
  • A wave is partially blocked by an obstacle.Two coherent waves are superposed.
  • Two coherent waves are superposed.
  • Two waves of equal speed and frequency are travelling through the same part of a medium
    in opposite directions.
The diagram shows a water wave passing through a gap in a harbour wall. The wavefronts curve
round the wall and reach a small boat in the harbour.
What is the name of this curving effect, and how can the gap be changed so that the wavefronts
do not reach the boat?

1646930_9aceec40883f4c23bab9feb50bea2d9a.png
  • Name of effect - diffraction, Change of the gap - make the gap slightly bigger
  • Name of effect - diffraction, Change of the gap - make the gap slightly smaller
  • Name of effect - refraction, Change of the gap - make the gap slightly bigger
  • Name of effect - refraction, Change of the gap - make the gap slightly smaller
The unit of intensity of polarization is _______.
  • $$C/m^2$$
  • $$C^2/m^2$$
  • $$C^2/m$$
  • $$m^2/C$$
What is not an essential condition for an observable interference pattern to occur between the waves two sources?
  • The frequencies of the two sources must be equal
  • The sources must be coherent
  • The sources must emit waves of equal amplitide
  • The waves from the two sources must overlap
A plane wavefront of wavelength $$\lambda$$ is incident on a single slit of width a. The angular width of principal maximum is?
  • $$\dfrac{\lambda}{a}$$
  • $$\dfrac{2\lambda}{a}$$
  • $$\dfrac{a}{\lambda}$$
  • $$\dfrac{a}{2\lambda}$$
The equation of a transverse wave is $$z=a\ \sin \left\{\omega t-\dfrac {k}{2}(x+y)\right\}$$ 
The equation of wavefront is :
  • $$x=$$ constant
  • $$y=$$ constant
  • $$x+y=$$ constant
  • $$y-x=$$ constant
If at the focus of a convex lens of focal length $$6$$ metre,a point source of $$36$$ condela is placed, then the illuminance on a screen placed normally to teh emergent beam of light is:
  • $$0$$ lux
  • $$6$$ lux
  • $$1$$ phot
  • $$6$$ phot
The geometrical path of a ray of light in a medium of refractive index $$2$$ is $$8\ m$$. The optical path is:
  • $$16\ m$$
  • $$8\ m$$
  • $$4\ m$$
  • $$none\ of\ these$$
Newton's rings are observed by keeping a spherical surface of $$100\ cm$$ radius on a plane glass plate. The wavelength of light used is $$5880\ \mathring{A}$$. If the diameter of the $$15th$$ bright ring is $$0.590\ cm$$, then diameter of the $$5th$$ ring is :
  • $$0.226\ cm$$
  • $$0.446\ cm$$
  • $$0.336\ cm$$
  • $$0.556\ cm$$
To obtain a good photographic print, an exposure of $$2s$$ at a distance of $$1\ m$$ from a $$75\ cd$$ bulb is done. To obtain an equally satisfactory result, what should be the distance, if time of exposure is $$12\ s$$ from a $$50\ cd$$ bulb?
  • $$1\ m$$
  • $$2\ m$$
  • $$3\ m$$
  • $$4\ m$$
Which of these waves can be polarised ?
  • Sound waves
  • Longitudinal waves on a string
  • Transverse waves on a string
  • Light waves
If the width of slit is gradually increased, it will be observed experimentally that :
  • bright fringes become reduced in intensity
  • bright fringes become increased in intensity
  • the intensity of minima is strictly zero
  • the fringes become more distinct
Which of the following quantities is not carried by light ?
  • Angular momentum
  • Linear momentum
  • Energy
  • None of the above
The wavefronts of a light coming from a distant source of unknown shape are nearly
  • plane
  • elliptical
  • cylindrical
  • spherical
Sources $$1$$ and $$2$$ emit lights of different wavelengths whereas $$3$$ and $$4$$ emit lights of different intensities. The coherence
  • can be obtained by sources $$1$$ and $$2$$
  • can be obtained by using sources $$3$$ and $$4$$
  • cannot be obtained by any of these sources
  • since contrast suffers when sources $$3$$ and $$4$$ are used so coherence cannot be obtained by using sources $$3$$ and $$4$$
Light is incident at an angle $$\phi$$ with the normal to a plane containing two slits of separation d. Select the expression that correctly describes the positions of the interference maxima in terms of the incoming angle $$\phi$$ and outgoing angle $$\theta$$.
1761456_9b9d290147b54165a8611acf1b2b1f22.PNG
  • $$sin\phi +sin\theta=\left(m+\dfrac{1}{2}\right)\dfrac{y}{d}$$
  • $$d sin \theta= m\lambda$$
  • $$ sin \phi-sin \theta=(m+1)\dfrac{\lambda}{d}$$
  • $$ sin \phi + sin \theta= m\dfrac{\lambda}{d}$$
A plane wavefront travelling in a straight line in a vacuum encounters a medium of refractive index $$m$$. At $$P$$, the shape of the wavefront is
1767090_18f7c0e9959c407584b7445e161bea41.PNG
In a YDSE with identical slits, the intensity of the central bright fringe is $$I_{0}$$. If one of the slits is covered, the intensity at the same point is
  • $$2I_{0}$$
  • $$I_{0}$$
  • $$I_{0}/2$$
  • $$I_{0}/4$$
If one of the two slits of a Young's double-slit experiment is painted so that it transmits half the light intensity as the second slit, then
  • the fringe system will altogether disappear
  • the bright fringes will become brighter and the dark fringes will become darker
  • both dark and bright fringes will become darker
  • dark fringes will become brighter and bright fringes darker
Light waves travel in vacuum along the y-axis. Which of the following may represent the wavefront?
  • $$ x= constant $$
  • $$y=constant$$
  • $$z=constant$$
  • $$x + y +z=constant$$
In a double-slit experiment, instead of taking slits of equal width, one slit is made twice as wide as the other. Then, in the interference pattern
  • the intensities of both the maxima and the minima increases
  • the intensities of maximum increases and the minima has zero intensity
  • the intensity of the maxima decreases and that of minima increases
  • the intensity of maxima decreases and the minima has zero intensity
Given figure shows two coherent sources $$S_{1}$$ and $$S_{2}$$ vibrating in same phase. AB is an irregular wire lying at a far distance from the sources $$S_{1}$$ and $$S_{2}$$. Let $$\dfrac{\lambda}{d}=10^{-3} \angle BOA ={0.12^\circ}$$. How many bright spots will be seen on the wire, including points $$A$$ and $$B$$?
1773460_d7ff384b1fa540548c8713bf86f1b43c.PNG
  • $$ 2 $$
  • $$3$$
  • $$4$$
  • more than 4
The slit $$1$$ of a Young's double-slit experiment is wider than slit $$2$$, so that the light from the slits are given as $$A_{1}=A_{0}$$ sin $$\omega t$$ and $$A_{2}=A_{3}A_{0}sin\left(\omega t+\dfrac{t}{3}\right)$$. The resultant amplitude and intensity, at a point where the path difference between them is zero, are $$A$$ and $$I$$, respectively. Then,
  • $$A=\sqrt{13}A_{0}$$
  • $$A=4A_{0}$$
  • $$I \alpha 16 A_{0}^{2}$$
  • $$I \alpha 13 A_{0}^{2}$$
If $$\beta$$ is the bandwidth, in Young's double slit experiment, the distance between the first dark hand and sixth bright band is:
  • $$5\dfrac{1}{2}\beta$$
  • $$6\beta$$
  • $$11\beta$$
  • $$5\beta$$
A bulb of $$100\ watt$$ is hanging at a height of one meter above the centre of a circular table of diameter $$4\ m$$. If the intensity at a point on its rim is $$I_0$$, then the intensity at the centre of the table will be
  • $$I_0$$
  • $$2 \sqrt 5I_0$$
  • $$2 I_0$$
  • $$5 \sqrt 5I_0$$
Colours of thin films result from or
On a rainy day, a small oil on water show brilliant colours. This is due to
  • Dispersion of light
  • Interference of light
  • Absorption of light
  • Scattering of light
Which of the following can not be polarised
  • Radio waves
  • Ultraviolet rays
  • Infrared rays
  • Ultrasonic waves
Young's experiment establishes that
  • Light consists of waves
  • Light consists of particles
  • Light consists of neither particles nor waves
  • Light consists of both particles and waves
By Huygens wave theory of light, we cannot explain the phenomenon of
  • Interference
  • Diffracton
  • Photoelectric effect
  • Polarisation
The resolving limit of healthy eye is about 
  • $$1'$$ or $$\left( \dfrac{1}{60}\right)^o$$
  • $$1"$$
  • $$1^o$$
  • $$\dfrac{1}{60}"$$
Out of the following statement which is not correct.
  • When unpolarised light passes through a Nicol's prism, the emergent light is elliptically polarised
  • Nicol's prism works on the principle of double refraction and total internal reflection
  • Nicol's prism can be used to produce and analyse polarised light
  • Calcite and Quartz are both doubly refracting crystals
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