CBSE Questions for Class 12 Medical Physics Wave Optics Quiz 6 - MCQExams.com

Sources 1 and 2 emit lights of different wavelengths whereas sources 3 and 4 emit lights of different intensities. The coherence
  • can be obtained by using 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 $$\theta$$

162923_daa2076694a646a1a416a5dc321f23ee.png
  • $$\sin { \phi } +\sin { \theta } =\left( m+\cfrac { 1 }{ 2 } \right) \cfrac { \lambda }{ d } $$
  • $$d\sin { \theta }=m\lambda$$
  • $$\sin { \phi } -\sin { \theta } =\left( m+1 \right) \cfrac { \lambda }{ d } $$
  • $$\sin { \phi } +\sin { \theta } =m\cfrac { \lambda }{ d } $$
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 increase
  • the intensity of the maxima increases and the minima has zero intensity
  • the intensity of the maxima decreases and that of the minima increases
  • the intensity of the maxima decreases and the minima has zero intensity
Consider an YDSE that has different slits width, as a result, amplitudes of waves from two slits are $$A$$ and $$2A$$, respectively. If $$I_{0}$$ be the maximum intensity of the interference pattern, then intensity of the pattern at a point where phase difference between waves is $$\phi$$ is :
  • $$I_{0}\cos^{2}\phi$$
  • $$\dfrac {I_{0}}{3}\sin^{2}\dfrac {\phi}{2}$$
  • $$\dfrac {I_{0}}{9}[5 + 4\cos \phi]$$
  • $$\dfrac {I_{0}}{9}[5 + 8\cos \phi]$$
In Young's interference experiment, if the slits are of unequal width, then
  • no fringes will be formed
  • the positions of minimum intensity will not be completely dark
  • bright fringe as displaced from the original central position
  • distance between two consecutive dark fringes will not be equal to the distance between two consecutive right fringes.
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 maxima and the minima increases
  • the intensity of maximum increase and minima has zero intensity
  • the intensity of the maxima decreases and that of minima increases
  • the intensity of the maxima decreases and the minima has zero intensity
If the path difference between the slits $${S}_{1}$$ and $${S}_{2}$$ is $$\lambda$$, the central fringe will have an intensity of
  • $$0$$
  • $${a}^{2}$$
  • $$2{a}^{2}$$
  • $$4{a}^{2}$$
One of the two slits in YDSE is painted over, so that it transmits only light waves having intensity half of the intensity of the light waves having half of the intensity of the light waves through the other slit. As a result of this
  • fringe pattern disappears
  • bright fringes become brighten and dark ones become darker
  • dark and bright fringes get fainter
  • dark fringes get brighter and bright fringes get darker
Instead of using two slits, if we use two separate identical sodium lamps in Young's experiment, which of the following will occur?
  • General illumination
  • Widely separate interference
  • Very bright maxima
  • Very dark minima
Resolving power of a telescope increases with
  • increase in focal length of eye-piece
  • increase in focal length of objective
  • increase in aperture of eye piece
  • increase in aperture of objective
An astronomical telescope has a large aperture to
  • reduce spherical aberration
  • have high resolution
  • increases span of observation
  • have low dispersion
Two sources of light are said to be coherent, when they give light waves of same
  • amplitude and phase
  • wavelength and constant phase difference
  • intensity and wavelength
  • phase and speed
Astronauts look down on earth surface from a space ship parked at an altitude of $$500$$ km. They can resolve object of the earth of the size (It can be assumed that the pupils diameter is 5 mm and wavelength of light is $$500$$ nm)
  • $$0.5 m$$
  • $$5 m$$
  • $$50 m$$
  • $$500 m$$
Which of the following is not essential for two sources of light in Young's double slit experiment to produce a sustained interference?
  • Equal wavelength
  • Equal intensity
  • Constant phase relationship
  • Equal frequency
Statement-1: All points on a wavefront vibrate in same phase with same frequency
Statement-2: Two sources are said to be coherent if they produce waves of same frequency with a constant phase difference.
  • Statement-1 is false, Statement -2 is true
  • Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1
  • Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for statement-1
  • Statement-1 is true, Statement-2 is false
Wavelength of light used in an optical instrument are $$\lambda_1 = 4000 A^o  and \lambda_2 = 5000 A^0$$, then ratio of their respective resolving powers (corresponding to $$\lambda_1   \ and  \ \lambda_2$$) is
  • 16:25
  • 9:1
  • 4:5
  • 5:4
In Young's double slit experiment, one slit is covered with red filter and another slit is covered by green filter, then interference pattern will be
  • red
  • green
  • yellow
  • invisible
Light transmitted by nicol prism is
  • unpolarised
  • plane polarised
  • circular polarised
  • elliptically polarised
A plane wave of wavelength 6250 $$\overset{o}{A}$$ is incident normally on a slit of width 2 $$\times$$ 10$$^{-2}$$ cm. The width of the principal maximum on a screen distant 50 cm will be
  • 312.5 $$\times$$ 10$$^{-3}$$ cm
  • 32.5 $$\times$$ 10$$^{-3}$$ m
  • 312.5 $$\times$$ 10$$^{-3}$$ m
  • 312 m
In the phenomena of diffraction of light, when blue light is used in the experiment in spite of red light, then
  • fringes will become narrower
  • fringes will become broader
  • no change in fringe width
  • None of these
Ray optics is valid, when characteristics dimensions are .......
  • of the same order as the wavelength of light.
  • much smaller than the wavelength of light.
  • of the order of one millimeter
  • much larger than the wavelength of light.
The condition for obtaining secondary maxima in the diffraction pattern due to single slit is (symbols have their usual meaning)
  • a sin $$\theta$$ = n$$\lambda$$
  • a sin $$\theta$$ = (2n - 1) $$\displaystyle\frac{\lambda}{2}$$
  • a sin $$\theta$$ = (2n - 1) $$\lambda$$
  • a sin $$\theta$$ = $$\displaystyle\frac{n\lambda}{2}$$
The limit of resolution of eye is approximately
  • $$1^0$$
  • $$1'$$
  • $$1 mm$$
  • $$1 cm$$
Light waves can be polarised because they
  • have high frequencies
  • have short wavelength
  • are transverse
  • can be reflected
Angular width of central maxima of a diffraction pattern of a single slit does not depend upon
  • Distance between slit and source
  • Wavelength of the light used
  • Width of slit
  • Frequency of light used
Four light waves are represented by
(i) y = $$a_1$$ sin $$\omega $$t      (ii) y = $$a_2$$ sin ( $$\omega $$t + $$\varepsilon)$$
(iii) y = $$a_1$$ sin 2$$\omega $$t  (iv) y = $$a_2$$ sin 2( $$\omega $$t + $$\varepsilon)$$
We obtain sustained interference due to super-position of
  • (i) and (ii)
  • (i) and (iii)
  • (ii) and (iv)
  • (iii) and (iv)
A slit of width a is illuminated by the red light of wavelength $$6500 {A}^0$$. If the first minimum falls at $$\theta$$ = 30$$^{o}$$, the value of a is
  • $$6.5 \times 10^{-4} mm$$
  • $$1.3 micron$$
  • $$3250 {A}^0$$
  • $$2.6 \times 10^{-4}cm$$
The contrast in the fringes in an interference pattern depends on 
  • fringe width
  • wavelength
  • intensity ratio of the sources
  • distance between the slits
The waveforms of a light wave traveling in vacuum are given by $$x+y+z=c$$.The angle made by the direction of propagation of light with the $$X$$-axis is
  • $$0^{o}$$
  • $$45^{o}$$
  • $$90^{o}$$
  • $$cos^{-1}\displaystyle\frac{1}{\sqrt{3}}$$
For interference to take place
  • sources must be coherent
  • sources must have same amplitude
  • waves should travel in opposite directions
  • sources must have same frequency
A slit of width $$a$$ is illuminated by white light. The first minimum for red light ($$\lambda$$ = 6500 $$\overset{o}{A}$$) will fall at $$\displaystyle\theta$$ = 30$$^{o}$$ when $$a$$ will be
  • 3250 $$\overset{o}{A}$$
  • 6.5 $$\times$$ 10$$^{-4}$$
  • 1.3 micron
  • 2.6 $$\times$$ 10$$^{-4}$$
When a compact disc is illuminated by small source of white light, coloured bands are observed. This is due to 
  • dispersion
  • diffraction
  • interference
  • reflection
Aperture of the human eye is 2 mm. Assuming the mean wavelength of light to be 5000 $$\overset{o}{A}$$, the angular resolution limit of the eye is nearly:
  • 2 minute
  • 1 minute
  • 0.5 minute
  • 1.5 minute
In case of an astronomical telescope, the distance between the objective lens and the eyepiece is equal to : 
(final image is at $$\displaystyle \infty $$)
  • $$\displaystyle { f }_{ o }+{ f }_{ e }$$
  • $$\displaystyle { f }_{ o }-{ f }_{ e }$$
  • $$\displaystyle \frac { { f }_{ o } }{ { f }_{ e } } $$
  • $$\displaystyle \frac { { f }_{ e } }{ { f }_{ o } } $$
The sum of the focal lengths of the objective and an eyepiece, in case of an astronomical telescope. is equal to : (final image is at $$\displaystyle \infty $$)
  • The length of the telescope
  • Half the length of the telescope
  • Double the length of the telescope
  • None of these
Which of the following phenomena can be demonstrated by light. But not with sound waves in an air column? 
  • Reflection
  • Diffraction
  • Refraction
  • Polarization
A plane wavefront $$AB$$ incident on a concave mirror as shown. Then, the wavefront just after reflection is
295212.PNG
  • None of the above
Which of the following is a unit for intensity of light?
  • Candle power
  • Lux
  • Both A & B
  • None of the above
The magnifying power of an astronomical telescope is $$8$$, then the ratio of the focal length of the objective to the focal length of the eyepiece is : (final image is at $$\displaystyle \infty $$)
  • $$8$$
  • $$\displaystyle \frac { 1 }{ 8 } $$
  • $$0.45$$
  • None of these
A satisfactory photographic print is obtained at a distance of 2 m from a 60 Cd lamp when the exposure time is 10s. The time of exposure required for the same quality print at a distance 4 m from a 120 Cd lamp is:
  • 5 s
  • 10 s
  • 20 s
  • 25 s
The phenomenon of interference is shown by:
  • longitudinal mechanical waves only
  • electromagnetic waves only
  • transverse mechanical waves only
  • all the above types of waves
A source of light suspended above a circular table at a height equal to the radius of the table gives an intensity I at the centre of the table, the intensity at the edge of the table would be (Assuming illuminance remains the same)
  • 0.25 I
  • 0.5 I
  • 0.7 I
  • 2.8 I
By corpuscular theory of light, the phenomenon which can be explained is ____________.
  • refraction
  • diffraction
  • interference
  • polarisation
The ratio of maximum and minimum intensities in an interference pattern is 36 :The ratio of the amplitudes of the two interfering waves will be
  • 5 : 7
  • 7 : 4
  • 4 : 7
  • 7 : 5
Which of the following phenomena can be demonstrated by light. But not with sound waves in an air column ?
  • Reflection
  • Diffraction
  • Refraction
  • Polarization
Wave front means:
  • all particles in it have same phase
  • few particles are in same phase, rest are in opposite phase
  • all particles have opposite phase of vibrations
  • all particles have random vibrations
Which of the following statements applies to light?
  • Light can only be described as particles.
  • Light can only be described as waves.
  • Light can be described as rays, waves and particles.
  • Light can only be described as rays.
A photographer changes the aperture of his camera and reduces it to half of the original aperture. The exposure time now should be:
  • same as before
  • double than before
  • four times than before
  • half than before
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:
  • $$\displaystyle \frac{\pi}{8}$$ radian
  • $$\displaystyle \frac{\pi}{4}$$ radian
  • $$\displaystyle \frac{\pi}{2}$$ radian
  • $$\pi$$ radian
An astronaut is looking down on earth's surface from a space shuttle an altitude of 400 km Assuming that the astronaut's pupil diameter is 5 mm and the wavelength of visible light is 500 nm, the astronaut will be able to resolve linear objects of the size of about :
  • 0.5m
  • 5m
  • 50m
  • 500m
0:0:1


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