JEE Questions for Physics Wave Optics Quiz 7 - MCQExams.com

In a Young\'s double slit experiment, the slit separation is 0.2 cm, the distance between the screen and slit is lm. Wavelength of the light used is 5000 Å. The distance between two consecutive dark fringes (in mm) is
  • 0.25
  • 0.26
  • 0.27
  • 0.28
In Young\'s double slit experiment, a minimum is obtained when the phase difference of super imposing waves is
  • Zero
  • (2n – 1)π
  • n π
  • (n +π
In Young\'s double slit experiment, the aperture screen distance is 2 m. The fringe width is 1 mm. Light of 600 nm is used. If a thin plate of glass (µ = 1.of thickness 0.06 mm is placed over one of the slits, then there will be a lateral displacement of the fringes by
  • 0 cm
  • 5 cm
  • 10 cm
  • 15 cm
If Fresnel\'s biprism experiment is held in water instead of air, then what will be the effect on fringe width?
  • Decreases
  • Increases
  • No effect
  • None of these
What is the effect on Fresnel\'s biprism experiment when the use of white light is made?
  • Fringe are affected
  • Diffraction pattern is spread more
  • Central fringe is white and all are coloured
  • None of the above
In Young\'s double slit experiment, the separation between the slit and the screen increases. The fringe width
  • Increases
  • Decreases
  • Remains unchanged
  • None of these
Young\'s double slit experiment is carrier out by using green, red and blue light, one colour at a time. The fringe widths recorded are βG, βR and βB, respectively. Then
  • βG > βB > βR
  • βB > βG > βR
  • βR > βB > βG
  • βR > βG > βB
In Young\'s double slit experiment, one of the slit is wider than other, so that amplitude of the light from one slit is double of that from other slit. If Im be the maximum intensity, the resultant intensity I when they interfere at phase difference ϕ is given by

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    Physics-Wave Optics-95559.png

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Assuming that universe is expanding, if the spectrum of light coming from a star which is going away from earth is tested, then in the wavelength of light
  • There will be no change
  • The spectrum will move to infrared region
  • The spectrum will seems to shift to ultraviolet side
  • None of the above
Doppler\'s effect in sound in addition to relative velocity between source and observer, also depends while source and observer or both are moving. Doppler effect in light depends only on the relative velocity of source and observer. The reason of this is
  • Einstein's mass-energy relation
  • Einstein's theory of relativity
  • Photoelectric effect
  • None of the above
A rocket is moving away from the earth at a speed of 6 × 107 m/s. The rocket has blue light in it. What will be the wavelength of light recorded by an observer on the earth? (wavelength of blue light = 4600 Å)
  • 4600 Å
  • 5520 Å
  • 3680 Å
  • 3920 Å
A spectral line λ = 5000 Å in the light coming from a distant star is observed as a 5200 Å. What will be recession velocity of the star?
  • 1.15 × 107 cm/s
  • 1.15 × 107 m/s
  • 1.15 × 107 km/s
  • 1.15 km/s
Three observes A, B and C measure the speed of light coming from a source to be vA, vB and v C. The observer A moves towards the source, the observer C moves away from the source with the same speed. The observer B stays stationary. The surrounding space is vacuum every where. Then
  • vA > vB > vC
  • vA < vB < vC
  • vA = vB = vC
  • vA = vB > vC
The velocity of light emitted by a source S observed by an observer O, who is at rest with respect to S is c. If the observer moves towards S with velocity v, the velocity of light as observed will be

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    Physics-Wave Optics-95566.png
  • c

  • Physics-Wave Optics-95567.png
In the context of Doppler effect in light, the term \'red shift\' signifies
  • Decrease in frequency
  • Increase in frequency
  • Decrease in intensity
  • Increase in intensity
The sun is rotating about its own axis. The spectral lines emitted from the two ends of its equator, for an observer on the earth, will show
  • Shift towards red end
  • Shift towards violet end
  • Shift towards red end by one line and towards violet and by other
  • No shift
A star is moving away from the earth with a velocity of 100 km/s. If the velocity of light is 3 × 108m/s then the shift of its spectral line of wavelength 5700 Å due to Doppler\'s effect will be
  • 0.63 Å
  • 1.90 Å
  • 3.80 Å
  • 5.70 Å
If a source of light is moving away from a stationary observer, then the frequency of light wave appears to change because of
  • Doppler's effect
  • Interference
  • Diffraction
  • None of these
A star emitting radiation at a wavelength of 5000 Å is approaching earth with a velocity of 1.5 × 106 m/s. The change in wavelength of the radiation as received on the earth, is
  • 25 Å
  • Zero
  • 100 Å
  • 2.5 Å
A star emitting light of wavelength 5896 Å is moving away from the earth with a speed of 3600 km/s. The wavelength of light observed on earth will
(c = 3 x 108 m/s is the speed of light)
  • Decrease by 5825.25 Å
  • Increase by 5966.75 Å
  • Decrease by 70.75 Å
  • Increase by 70.75 Å
A star moves away from earth at speed 0.8 c while emitting light of frequency 6 × 1014 Hz. What frequency will be observed on the earth? (in units of 1014 Hz) (c = speed of light)
  • 0.24
  • 1.2
  • 30
  • 3.3
A light source approaches the observer with velocity 0.8 c. The doppler shift for the light of wavelength 5500 Å is
  • 4400 Å
  • 1833 Å
  • –3666 Å
  • 7333 Å
A heavenly body is receding from earth such that the fractional change in λ is 1, then its velocity is

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  • 2)
    Physics-Wave Optics-95574.png

  • Physics-Wave Optics-95575.png

  • Physics-Wave Optics-95576.png
In the spectrum of light of a luminous heavenly body the wavelength of a spectral line is measured to be 4747 Å while actual wavelength of the line is 4700 Å. The relative velocity of the heavenly body with respect to earth will be (velocity of light is 3 × 108 m/s)
  • 3 × 103 m/s moving towards the earth
  • 3 × 103 m/s moving away from the earth
  • 3 × 106 m/s moving towards the earth
  • 3 × 106 m/s moving away from the earth
The wavelength of light observed on the earth, from a moving star is found to decrease by 0.05%. Relative to the earth the star is
  • Moving away with a velocity of 1.5 × 105 m/s
  • Coming closer with a velocity of 1.5 × 105 m/s
  • Moving away with a velocity of 1.5 × 104 m/s
  • Coming closer with a velocity of 1.5 × 104 m/s
A star is going away from the earth. An observer on the earth will see the wavelength of light coming from the star
  • Decreased
  • Increased
  • Neither decreased nor increased
  • Decreased or increased depending upon the velocity of the star
A star is moving towards the earth with a speed of 4.5 × 106 m/s. If the true wavelength of a certain line in the spectrum received from the star is 5890 Å, its apparent wavelength will be about [c = 3 × 108 m/s]
  • 5890 Å
  • 5978 Å
  • 5802 Å
  • 5896 Å
Due to Doppler\'s effect, the shift in wavelength observed is 0.1 Å for a star producing wavelength 6000 Å. Velocity of recession of the star will be
  • 2.5 km/s
  • 10 km/s
  • 5 km/s
  • 20 km/s
When the wavelength of light coming from a distant star is measured it is found shifted towards red. Then the conclusion is
  • The star is approaching the observer
  • The star recedes away from earth
  • There is gravitational effect on the light
  • The star remain stationary
The velocity of a moving galaxy is 300 km s–1 and the apparent change in wavelength of a spectral line emitted from the galaxy is observed as 0.5 nm. Then, the actual wavelength of the spectral line is
  • 3000 Å
  • 5000 Å
  • 6000 Å
  • 4500 Å
How fast a person should drive his car so that the red signal of light appears green?
(Wavelength for red colour = 6200 Å and wavelength for green colour = 5400 Å)
  • 1.5 × 108 m/s
  • 7 × 107 m/s
  • 3.9 × 107 m/s
  • 2 × 108 m/s
Two beams of light will not give rise to an interference pattern, if
  • They are coherent
  • They have the same wavelength
  • They are linearly polarized perpendicular to each other
  • They are not monochromatic
A parallel beam of fast moving electrons is incident normally on a narrow slit. A screen is placed at a large distance from the slit. It the speed of the electrons is increased, which of the following statement is correct
  • Diffraction pattern is not observed on the screen in the case of electrons
  • The angular width of the central maxima of the diffraction pattern will increase
  • The angular width of the central maxima will decrease
  • The angular width of the central maxima will remain the same
Consider Fraunhoffer diffraction pattern obtained with a single slit at normal incidence. At the angular position of first diffraction minimum, the phase difference between the wavelets from the opposite edges of the slit is
  • π / 4
  • π / 2
  • π
  • 2 π
Angular width (β) of central maximum of a diffraction pattern on a single slit does not depend upon
  • Distance between slit and source
  • Wavelength of light used
  • Width of the slit
  • Frequency of light used
In the experiment of diffraction at a single slit, if the slit width is decreased, the width of the central maximum
  • Increases in both Fresnel and Fraunhoffer diffraction
  • Decreases both in Fresnal and Fraunhoffer diffraction
  • Increases in Fresnel diffraction but decreases in Fraunhoffer diffraction
  • Decreases in Fresnel diffraction but increases is Fraunhoffer diffraction
Conditions of diffraction is

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    Physics-Wave Optics-95588.png

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  • None of these
The phenomenon of diffraction of light was discovered by
  • Huyghen
  • Newton
  • Fresnel
  • Grimaldi
In a diffraction pattern by a wire, on increasing diameter of wire, fringe width
  • Decreases
  • Increases
  • Remains unchanged
  • Increasing or decreasing will depend on wavelength
What will be the angular width of central maxima in Fraunhoffer diffraction when light of wavelength 6000 Å is used and slit width is 12 × 10–5 cm?
  • 2 rad
  • 3 rad
  • 1 rad
  • 8 rad
The diffraction effect can be observe in
  • Only sound waves
  • Only light waves
  • Only ultrasonic waves
  • Sound as well as light waves
When light is incident on a diffraction grating the zero order principal maximum will be
  • One of the component colours
  • Absent
  • Spectrum of the colours
  • White
In order to see diffraction the thickness of the film is
  • 100 Å
  • 10, 000 Å
  • 1 mm
  • 1 cm
Diffraction effects are easier to notice in the case of sound waves than in the case of light waves because
  • Sound waves are longitudinal
  • Sound is perceived by the ear
  • Sound waves are mechanical waves
  • Sound waves are of longer wavelength
Direction of the first secondary maximum in the Fraunhoffer diffraction pattern at a single slit is given by (a is the width of the slit)

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    Physics-Wave Optics-95594.png

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A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of incident beam. At the first maxima of the diffraction pattern the phase difference between the rays coming from the edges of the slit is
  • 0
  • π/2
  • π
  • 2 π
Diffraction and interference of light suggest
  • Nature of light is electro-magnetic
  • Wave nature
  • Nature of quantum
  • Nature of light is transverse
A light wave is incident normally over a slit of width 24 × 10–5 cm. The angular position of second dark fringe from the central maxima is 30°. What is the wavelength of light ?
  • 6000 Å
  • 5000 Å
  • 3000 Å
  • 1500 Å
The condition for observing Fraunhoffer diffraction from a single slit is that the light wavefront incident on the slit should be
  • Spherical
  • Cylindrical
  • Plane
  • Elliptical
To observe diffraction the size of an obstacle
  • Should be of the same order as wavelength
  • Should be much larger than the wavelength
  • Have no relation to wavelength
  • Should be exactly λ / 2
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