Namrata Das Exams Prep Master
Exams Prep Master
Wave optics, also referred to as Physical optics, deals with various phenomena such as polarization, diffraction, interference, and other occurrences where ray approximation of geometric optics cannot be done. This is the reason why the section of optics that deals with the behavior of light and its wave characteristics is said to be wave optics. The approximation, in wave optics, is carried out by using ray optics for the estimation of the field on a surface.
Moreover, it comprises integrating a ray-estimated field over a mirror, lens, or aperture for the calculation of the scattered or transmitted field. Wave optics is one of the most significant aspects of class 12 physic. In this article, we will discuss the MCQ-type questions related to wave optics with their correct answers. These MCQ questions will also help you to study the concept of wave optics thoroughly.
Ques: State the essential condition for diffraction of light to occur.
a) The size of the aperture must be less when compared to the wavelength of light
b) The size of the aperture must be more when compared to the wavelength of light
c) The size of the aperture must be comparable to the wavelength of light
d) The size of the aperture should not be compared to the wavelength of light
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Ans: Option c is the correct answer.
Explanation: Diffraction is basically about spreading out of the waves while they pass through an aperture or around objects. Hence, when the size of the obstacle or the aperture is comparable to the wavelength of light, it is the essential condition for diffraction of light to occur. Thus, option c would be the answer.
Ques: What is the cause of diffraction?
a) Interference of primary wavelets
b) Interference of secondary wavelets
c) Reflection of primary wavelets
d) Reflection of secondary wavelets
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Ans: Option b is the correct answer.
Explanation: Diffraction happens due to the interference of secondary waves in different portions of a wavefront. When it is allowed to pass across a small aperture and obstacle. Now, this interference can be either constructive or destructive as well. Hence, the answer is the interference of secondary wavelets.
Ques: What should be the order of the size of an obstacle or aperture for diffraction light?
a) Order of wavelength of light
b) Order of wavelength of obstacle
c) Order in ranges of micrometer
d) Order in ranges of nanometer
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Ans: Option a is the correct answer.
Explanation: The size of an obstacle or aperture for diffraction light can neither be in ranges of micrometer nor the nanometer. Thus, the Order of wavelength of light should be the order of the size of an obstacle or aperture for diffraction light.
Ques: A small circular disc is placed in the path of light from a distant source. Identify the nature of the fringe produced.
a) Dual
b) Narrow
c) Dark
d) Bright
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Ans: Option d is the correct answer.
Explanation: Waves from a source at a distance are usually diffracted by the edge of the provided disc. These diffracted waves interfere constructively at the center point of the shadow. Consequently, they produce a bright fringe. Therefore, bright would be the nature of the fringe produced.
Ques: Single slit diffraction is completely immersed in water without changing any other parameter. How is the width of the central maximum affected?
a) Insignificant
b) Increases
c) Decreases
d) Becomes zero
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Ans: Option c is the correct answer.
Explanation: The wavelength of the light in water decreases due to its complete immersion in the water. Hence, the width of the central maximum would decrease. This impact is due to the effect on the width of the central maximum when a single slit is completely immersed in water.
Ques: Diffraction is common in light waves.
a) True
b) False
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Ans: option b is the correct answer.
Explanation: The wavelength of light is much smaller than the size of any objects present around us. Hence, the diffraction of light cannot easily be seen. Therefore an obstacle or aperture of the size of the wavelength of light of the wave is required for the diffraction of a wave. As the wavelength of light is of the order of 10-6m and obstacle or aperture of this size is rare, diffraction is not common in light waves. Hence, the statement is false.
Ques: What will be the linear width of the central maximum on a screen that is kept 5 m away from the slit, if a light of wavelength 800 nm strikes a slit of 5 mm width.
a) 1.2 mm
b) 5.6 mm
c) 6.5 mm
d) 9.7 mm
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Ans: option a is the correct answer.
Explanation: Already given: d = 5mm, wavelength = 800.
Linear width will be calculated by this formula as:
β0 = 2Dλd
Putting the values...
β0 = (2×5×800×10−9)(5×10−3)
β0 = 1.6 × 10-3 m
β0 = 1.6 mm
Thus, the linear width of the central maximum on a screen that is kept 5 m away from the slit is 1.6 mm.
Ques: In young’s double-slit experiment, the width of the fringes obtained when the light of wavelength 6000 È? is 2. 0 mm. What will be the fringe width if the entire apparatus is immersed in a liquid of refractive index 1.33?
a) 0.5 mm
b) 1.0 mm
c) 1.5 mm
d) 2.0 mm
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Ans: Option c is the correct answer.
Explanation: Let, β’ be the fringe width when the whole apparatus is inside water. And β be the fringe width when the entire apparatus is in air. Hence, 1.5 mm is the correct answer.
Ques: A monochromatic light of wavelength 5100 È? from a narrow slit is incident on a double slit. If the overall separation of 10 fringes on a screen 200 cm away is 2 cm then, the separation between the slit is
a) 1.10 mm
b) 0.51 mm
c) 0.22 mm
d) 0.11 mm
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Ans: option b is the correct answer.
Explanation: Let, d be the separation between the slits and d what is the distance between the slits and screen. The wavelength of the light used is denoted by λ.
Already provided, d = 200 cm, λ = 5100 A
Put these values into the formula and the answer will be 0.51 mm.
Ques: Consider interference between two waves from two sources of intensities I and 4I. What is the ratio of intensities at the point where the phase difference is π?
a) I
b) 9 I
c) 5 I
d) 9 I
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Ans: Option a is the correct answer.
Explanation: A point where two waves of amplitudes a1 and a2 meet with a phase difference of Ï?, the resultant intensity at this point is denoted by:
IR = a12 + a22 +2 a1a2cos Ï?.
Given, a1 = I, a2 = 4I and Ï? = π
The intensity of a wave is directly proportional to the square of its amplitude. Hence, the answer is I.
Ques: The polarizing angle for a medium is 60o. The critical angle for this medium is
a) sin-1 (0.321)
b) sin-1 (0.577)
c) sin-1 (0.732)
d) sin-1 (1)
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Ans: Option b is the correct answer.
Explanation: According to the Brewster’s law,
the refractive of the medium is shown as,
μ = tan ip = tan 60o
= 1.732.
Now, take C as the critical angle for the medium, therefore,
μ = 1/ sin C
sin C = 1/ μ = 1/1.732 = 0.577
C = sin-1 (0.577).
Ques: Resolving power of telescope can be increased by increasing
(a) the wavelength
(b) the diameter of the objective
(c) the diameter of the eyepiece
(d) the focal length of the eyepiece
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Ans: Option b is the correct answer.
Explanation: The diameter of the objective, and not an eyepiece or the wavelength, as R.P. of a telescope = D1.22λ
R.P. is directly proportional to 1.22 A to the diameter of the objective (D). Hence, option b is correct.
Ques: Polarization of light proves
(a) the corpuscular nature of light.
(b) quantum nature of light.
(c) transverse wave nature of light.
(d) longitudinal wave nature of light.
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Ans: Option c is the correct answer.
Explanation: Transverse wave nature of light is shown as the polarization of light. Simultaneously, the polarization of light proves the transverse wave nature of light. Hence, option c is correct.
Ques: The wavefront due to a source situated at infinity is
(a) spherical
(b) cylindrical
(c) planar
(d) circular
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Ans: Option c is the correct answer.
Explanation: The wavefront due to any source situated at infinity is always planar and not cylindrical, spherical, or circular. Hence, option c is correct.
Ques: A laser beam is coherent because it contains
(a) waves of several wavelengths.
(b) incoherent waves of a single wavelength.
(c) coherent waves of several wavelengths
(d) coherent waves of a single wavelength.
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Ans: option d is the correct answer.
Explanation: Coherent waves of a single wavelength are responsible for the coherence of a laser beam. Hence, option d would be correct.
Ques: According to Huygens’ principle, light is a form of
(a) particle
(b) rays
(c) wave
(d) radiation
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Ans: option d is the correct answer.
Explanation: According to Huygens’ principle, travel of the light is in the form of a longitudinal wave i.e., radiation. Hence, option d would be correct.
Ques: Two coherent monochromatic light beams of intensities I and 41 superimpose. The maximum and minimum possible intensities in the resulting beam are:
(a) 5I and I
(b) 5I and 3I
(c) 3I and I
(d) 9I and I
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Ans: option d is the correct answer.
Explanation:
Imax = I1 + I2 + 2√I1 x I2 = 9I
Imin = I1 + I2 - 2√I1 x I2 = I
Hence, option d 9I and I would be the correct answer.
Ques: When exposed to sunlight, thin films of oil on water of the ten exhibit brilliant colors due to the phenomenon of
(a) interference
(b) diffraction
(c) dispersion
(d) polarization
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Ans: Option a is the correct answer.
Explanation: Interference is an effect to talk about the phenomenon that takes place when thin films of oil on water of the ten exhibit brilliant colors. Hence, option a would be the correct answer.
Ques: What happens if the monochromatic light used in Young’s double-slit experiment is replaced by white light?
(a) No fringes are observed.
(b) All bright fringes become while.
(c) All bright fringes have colors between violet and red.
(d) Only the central fringe is white and all other fringes are colored.
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Ans: Option d is the correct answer.
Explanation: If the monochromatic light used in Young’s double-slit experiment is replaced by white light then it shows that only the central fringe is white and all other fringes are colored.
Ques: When a compact disk is illuminated by a source of white light, colored lines are observed. This is due to
(a) dispersion
(b) diffraction
(c) interference
(d) refraction
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Ans: Option b is the correct answer.
Explanation: Diffraction is the reason when a compact disk is illuminated by a source of white light, colored lines are observed.
Ques: When an unpolarized light beam is an incident from the air onto glass (n = 1.5) at the polarizing angle.
(a) The reflected beam is polarized completely
(b) Reflected and refracted beams are partially polarised
(c) Refracted beam is plane-polarized
(d) the Whole beam of light is refracted
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Ans: Option b is the correct answer.
Explanation: Reflected and refracted beams are partially polarised when an unpolarised light beam is an incident from the air onto glass (n = 1.5) at the polarizing angle.
Ques: Two periodic waves of intensities I1 and I2 pass through a region at the same time in the same direction. The sum of maximum and minimum intensities is:
(a) (I1 + I2)
(b) 2 (I1 + I2)
(c) (I1 + I2)
(d) 2 (I1 + I2)
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Ans: option b is the correct answer.
Explanation: Imax = I1 + I2 + 2√I1 x I2 =
Imin = I1 + I2 - 2√I1 x I2 =
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