JEE Questions for Physics Wave Optics Quiz 4 - MCQExams.com

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. If 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 maximum of the diffraction pattern will increase
  • The angular width of the central maximum will decrease
  • The angular width of the central maximum will remains the same
A single slit Fraunhofer diffraction pattern is formed with white light. For what wavelength of light the third secondary maximum in the diffraction pattern coincides with the second secondary maximum in the pattern for red light of wavelength 6500 Å?
  • 4400 Å
  • 4100 Å
  • 4642.8 Å
  • 9100 Å
If I0 is the intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity when the slit width is doubled ?
  • 2I0
  • 4I0
  • I0
  • I0 / 2
A single slit of width d is illuminated by violet light of wavelength 400 nm and the width of the diffraction pattern is measured as y. When half of the slit width is covered and illuminated by yellow light of wavelength 600 nm., the width of the diffraction pattern is
  • the pattern vanishes and the width is zero
  • y/3
  • 3y1
  • None of these
Two beams, A and B of plane polarised light with mutually perpendicular planes of polarisation 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° makes the two beams appear equally bright. If the initial intensities of the two beams are IA and IBrespectively, then IA / IB equals.
  • 3
  • 2)
    Physics-Wave Optics-95377.png
  • 1

  • Physics-Wave Optics-95378.png
Find the final intensity of light (I ''), if the angle between the axes of two polaroids is 60°
Physics-Wave Optics-95379.png

  • Physics-Wave Optics-95380.png
  • 2)
    Physics-Wave Optics-95381.png

  • Physics-Wave Optics-95382.png

  • Physics-Wave Optics-95383.png
Diameter of the objective of a telescope is 200 cm. What is the resolving power of telescope? (take, wavelength of light = 500 Å)
  • 6.56 × 105
  • 3.28 × 105
  • 1 × 106
  • 3.28 × 106
A ray of light is incident at polarising angle such that its deviation is 24°, then angle of incidence is
  • 24 °
  • 57 °
  • 66 °
  • 90 °
A 20 cm length of a certain solution causes right handed rotation of 38°. A 30 cm length of another solution causes left handed rotation of 24°. The optical rotation caused by 30 cm length of a mixture of the above solutions in the volume ratio 1 : 2 is
  • left handed rotation of 14°
  • right handed rotation of 14°
  • left handed rotation of 3°
  • right handed rotation of 3°
If the polarising angle of a piece of glass for green light is 54.74°, then the angle of minimum deviation for an equilateral prism made of same glass is (Given, tan 54.74° = 1.
  • 45°
  • 54.74°
  • 60°
  • 90°
  • 30°
Specific rotation of sugar solution is 0.5 deg m2/kg. 200 kg m-3 of impure sugar solution is taken in a sample polarimeter tube of length 20 cm and optical rotation is found to be 19°. The percentage of purity of sugar is
  • 20%
  • 80%
  • 95%
  • 89%
H-polaroid is prepared by
  • orienting herapathite crystal in the same direction in nitrocellulose
  • using thin tourmaline crystals
  • stretching polyvinyl alcohol and then heated with dehydrating agent
  • stretching polyvinyl alcohol and then impregnating with iodine
When unpolarised light beam is incident from air onto glass (n =1.at the polarising angle
  • reflecttd beam is polarised 100 percent
  • reflected and refracted beams are partially polarised
  • the reason for (a) is that almost all the light is reflected
  • All of the above
The correct curve between the energy of photon (E) and its wavelength (λ) in Fig. is

  • Physics-Wave Optics-95386.png
  • 2)
    Physics-Wave Optics-95387.png

  • Physics-Wave Optics-95388.png

  • Physics-Wave Optics-95389.png
In Young’s expt, the distance between two slits is d/3 and the distance between the screen and the slits is 3 D. The number of fringes in 1/3m on the screen, formed by monochromatic light of wavelength 3 λ, will be

  • Physics-Wave Optics-95391.png
  • 2)
    Physics-Wave Optics-95392.png

  • Physics-Wave Optics-95393.png

  • Physics-Wave Optics-95394.png
In the set up shown in Fig the two slits, S1 and S2 are not equidistant from the slit S. The central frings at o is then
Physics-Wave Optics-95396.png
  • always bright
  • always dark
  • either dark or bright depending on the position of S
  • neither dark nor bright
In Young’s double slit experiment, the two equally bright slits are coherent, but of phase difference π/3. If maximum intensity on the screen is I0, the intensity at the point on the screen equidistant from the slit is
  • I0
  • I0/2
  • I0/4
  • 3I0/4
In an interference pattern produced by two identical slits, the intensity at the site of the central maximum is I. The intensity at the same spot when either of the two slits is closed is I0.Therefore
  • I = I0
  • I = 2I0
  • I = 4I0
  • I and I0 are not related to each other
Interference fringes are being produced on screen XY by the slits S1 and S2. In fig the correct fringe locus is
Physics-Wave Optics-95398.png
  • PQ
  • W1 W2
  • W3 W4
  • XY
In Young’s double slit experiment let S1 and S2 be the two slits, and C be the centre of the screen. If ∠S1CS2 = θ and λ is the wavelength, the fringe width will be

  • Physics-Wave Optics-95399.png
  • 2)
    Physics-Wave Optics-95400.png

  • Physics-Wave Optics-95401.png

  • Physics-Wave Optics-95402.png
Light of wavelength λ in air enters a medium of refractive index μ. Two points in this medium, lying along the path of this light are at a distance x apart. The phase difference between these points is

  • Physics-Wave Optics-95404.png
  • 2)
    Physics-Wave Optics-95405.png

  • Physics-Wave Optics-95406.png

  • Physics-Wave Optics-95407.png
A parallel beam of light of wavelength 5000 Å is incident normally on a single slit of width 0.001 mm. The light is focussed by a convex lens on a screen placed in focal plane. The first minimum is formed for the angle of diffraction equal to
  • 0o
  • 15o
  • 30o
  • 60o
The position of the direct image obtained at O, when a monochromatic beam of light is passed through a plane transmission grating at normal incidence is shown in Fig. The diffracted images A, B and C correspond to the first, second and third order diffraction when the source is replaced by another source of shorter wave – length
Physics-Wave Optics-95410.png
  • all the four will shift in the direction C to O
  • all the four will shift in the direction O to C
  • the images C, B and A will shift towards O
  • The images C,B and A will shift away form O
Light of wavelength 5000 Å is incident normally on a slit. The first minimum of the diffraction pattern is formed at a distance of 5 mm from central maximum.The screen is situated at distance of 2 m from the slit. The slit width is
  • 0.2 mm
  • 0.8 mm
  • 0.4 mm
  • 2.0 mm
A calcite crystal is placed over a dot on a piece of paper and rotated. On viewing through calcite, one will see
  • a single dot
  • two stationary dots
  • two rotating dots
  • one dot rotating about the other
A star is moving away from the earth with a velocity of 100 km/s. if velocity of light is 3 × 108 m/s then the shift of its spectral line of wavelength 5700 Å due to Dopper’s effect will be
  • 0.63 Å
  • 1.900 Å
  • 3.80 Å
  • 5.70 Å
Ray optics is valid, when characteristic dimensions are
  • Much smaller than the wavelength of light
  • Much larger than the wavelength of light
  • Of the same order as the wavelength of light
  • Of the order of one millimetre
Wavelength of light of frequency 100 Hz is
  • 2 × 106 m
  • 3 × 106 m
  • 4 × 106 m
  • 5 × 106 m
In Young’s double slit expt., 12 fringes are obtained to be formed in a certain segment of the screen when light of wavelength 600 nm is used. If the wavelength of light is changed to 400 nm, umber of the fringes observed in the same segment of the screen is given by
  • 12
  • 18
  • 24
  • 30
Two beams of light having intensities I and 4I interfere to produce a fringe pattern on a screen. The phase difference between the beams is π/2 at point A and π at point B. Then the difference between the resultant intensities at A and B is
  • 2 I
  • 4 I
  • 5 I
  • 7 I
Angular width (θ) of central maximum of a diffraction pattern of 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 Young’s double slit experiment, the wavelength of light was changed from 7000 Å to 3500 Å. While doubling the separation between the slits,which of the following is not true for this expt.?
  • The width of fringes changes
  • The colour of bright fringes changes
  • The separation between successive bright fringes changes
  • The separation between successive dark fringes remains unchanged
To demonstrate the phenomenon of interference, we require two sources, which emit radiations
  • of nearly same frequency
  • of the same frequency
  • of different wavelengths
  • of the same frequency and having a definite phase relationship.
Interference fringes are produced in Young’s double slit experiment using light of wavelength 5000 Å .when a film of material 2.5 × 10-3 m thick was placed over 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
  • 1.33
  • 1.4
  • 1.5
If two coherent sources are placed at a distance 3 λ from each other, symmetric to the centre of the circle shown in fig (R>>λ), then number of bright fringes shown on the screen placed along the circumference is
Physics-Wave Optics-95419.png
  • 16
  • 12
  • 8
  • 4
White light is used to illuminate the two slits in a young’s double slit expt. The separation between slits is b and the screen is at a distance d (>>b) from the slits. At a point on the screen directly in front of one of the slits, certain wavelengths are missing, fig. Some of these missing wavelengths are
Physics-Wave Optics-95421.png
  • λ/b2/d
  • λ2b2/d
  • λ = b2/3d
  • λ = 2b2/3d
The two coherent sources with intensity ratio β produce interference. The fringe visibility will be

  • Physics-Wave Optics-95423.png
  • 2)
    Physics-Wave Optics-95424.png

  • Physics-Wave Optics-95425.png

  • Physics-Wave Optics-95426.png
In a biprism expt, 5th dark fringe is obtained at a point. If a thin transparent film is placed in the path of one of waves, then 7th bright fringe is obtained at the same point. The thickness of the film in terms of wavelength λ and refractive index μ will be

  • Physics-Wave Optics-95428.png
  • 2)
    Physics-Wave Optics-95429.png

  • Physics-Wave Optics-95430.png

  • Physics-Wave Optics-95431.png
A monochromatic beam of light falls on young’s double slit expt. Apparatus at some (say θ) as shown in fig . A thin sheet of glass is inserted infront of the lower slit S2. The central bright fringe (path difference=will be obtained
Physics-Wave Optics-95433.png
  • any where depending on angle θ thickness of plate t and refractive index of glass μ
  • at O
  • below O
  • above O
Light of wavelength λ is incident on a slit of width d. The resulting diffraction pattern is observed on a screen at a distance D. The linear width of the principal maximum is equal to the width of the slit, if D equals

  • Physics-Wave Optics-95434.png
  • 2)
    Physics-Wave Optics-95435.png

  • Physics-Wave Optics-95436.png

  • Physics-Wave Optics-95437.png
A plate of thickness t made of a material of refractive index μ is placed in front of one of the slits in a double slit experiment. What should be the minimum thickness t, which will make the intensity at the centre of the fringe pattern zero?

  • Physics-Wave Optics-95439.png
  • 2)
    Physics-Wave Optics-95440.png

  • Physics-Wave Optics-95441.png

  • Physics-Wave Optics-95442.png
By corpuscular theory of light, the phenomenon which can be explained is
  • Refraction
  • Interference
  • Diffraction
  • Polarisation
According to corpuscular theory of light, the different colours of light are due to
  • Different electromagnetic waves
  • Difference force of attraction among the corpuscles
  • Different size of the corpuscles
  • None of the above
Huygen\'s conception of secondary waves
  • Allow us to find the focal length of a thick lens
  • Is a geometrical method to find a wavefront
  • Is used to determine the velocity of light
  • Is used to explain polarization
The idea of the quantum nature of light has emerged in an attempt to explain
  • Interference
  • Diffraction
  • Radiation spectrum of a black body
  • Polarization
Two coherent sources of light can be obtained by
  • Two different lamps
  • Two different lamps but of the same power
  • Two different lamps of same power and having the same colour
  • None of the above
Light appears to travel in straight lines since
  • It is not absorbed by the atmosphere
  • It is reflected by the atmosphere
  • Its wavelength is very small
  • Its velocity is very large
The idea of secondary wavelets for the propagation of a wave was first given by
  • Newton
  • Huygen
  • Maxwell
  • Fresnel
By a monochromatic wave, we mean
  • A single ray
  • A single ray of a single colour
  • Wave having a single wavelength
  • Many rays of a single colour
The similarity between the sound waves and light waves is
  • Both are electromagnetic waves
  • Both are longitudinal waves
  • Both have the same speed in a medium
  • They can produce interference
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