JEE Physics Wave Optics MCQs Set B

Question: In Young's double slit experiment, when two light waves form third minimum, they have

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  To observerve diffraction the size of an obstacle

• a) Should be of the same order as wavelength
• b) Should be much smaller than the wavelength
• c) Has no relation to wavelength
• d)

  

Answer: Should be of the same order as wavelength

Question: If frequency of light wave propagating in water is halved, its speed

• a) Remains same
• b) Becomes four times
• c) Is halved
• d) Is doubled

Answer: Remains same

Question:  White light is used in Young’s double slit experiment. Separation between slits is y and the screen is atdistance x from slits (x >> y). Which of these wavelengths is missing in front of one of the slits?

• a)

  

• b)

  

• c)

  

• d) All of these

Answer:

Question: Corpuscular theory of light predicts speed of light to be

• a) Greater in water than in vacuum
• b) Dependent on intensity of light
• c) Greater in vacuum than in water
• d) Independent of medium

Answer: Greater in water than in vacuum

Question:

• a) Circular
• b) Hyperobic
• c) Elliptical
• d) Parabolic

Answer: Circular

Question: In Fraunhoffer diffraction from a single slit, wave front incident on the slit is

• a) Planar
• b) Spherical
• c) Cylindrical
• d) Either spherical or cylindrical

Answer: Planar

Question: Young’s double slit experiment is performed with monochromatic light. A thin film is introduced in front of one of the slits

• a) Intensity at position of first maxima may decrease
• b) Central maxima may remain unshifted
• c) Intensity at the position of central maxima may increase
• d) Intensity at the position of central maxima must decrease

Answer: Intensity at position of first maxima may decrease

Question: Apparent wavelength of light coming from a star moving away from earth is 0.02% more than its actual wavelength. Velocity of star is

• a) 60 km/s
• b) 30 km/s
• c) 90 km/s
• d) 120 km/s

Answer: 60 km/s

Question: Diffraction is easily noticeable for sound waves than for light waves because sound waves

• a) Have longer wavelength
• b) Are high energy waves
• c) Are low intensity waves
• d) Are mechanical in nature

Answer:  Have longer wavelength

Question:  In the Young’s arrangement, screen starts moving towards right with constant speed v. Initial distance between screen and plane of slits is x. At t = 0, 1st order maxima is lying at point A. After how much time first order minima lies at point A?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  Unpolarized light of intensity x is incident on a polarising sheet. Intensity of light which does not get transmitted is

• a)

  

• b)

  

• c) x
• d) Zero

Answer:

Question:   Light of wavelength l is coming from a star. What is the limit of resolution of a telescope whose objective has diameter r ?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Approximate thickness of oil film to observe interference of light (due to which it looks coloured) is

• a) 10^–3 mm
• b) 10 pm
• c) 1 cm
• d) 10 mm

Answer: 10^–3 mm

Question: Slit widths in a Young’s double slit experiment are in the ratio 9 : 4. Ratio of intensity at minima to that at maxima is

• a) 1 : 25
• b) 1 : 16
• c) 16 : 81
• d) 4 : 9

Answer: 1 : 25

Question: Width of slit in a single slit diffraction experiment such that 20 maxima of double slit interference pattern are obtained within central maxima of the diffraction pattern is (Slit separation for double slit arrangement = 2 mm)

• a) 0.2 mm
• b) 0.4 mm
• c) 0.1 mm
• d) 0.05 mm

Answer: 0.2 mm

Question: In Fraunhoffer diffraction, at the angular position of first diffraction minimum, phase difference (in radian) between wavelets from opposite edges of the slit is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Choose the correct alternative

• a)

  

• b)  Natural light from sun is polarised
• c)  Refracted light, when light is incident at Brewster angle, is linearly polarised
• d)  When plane polarised light passes through polaroid, it changes its nature to linearly polarised

Answer: 

Question: A star, which is emitting radiation at a wavelength of 5000 Å, is approaching the earth with a velocity of 1.5 × 10⁵ m/s. The change in wavelength of the radiation as received on the earth is

• a) 2.5 Å
• b) Zero
• c) 100 Å
• d) 25 Å

Answer: 2.5 Å

More Questions..............................

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) The intensity gradually reduces to zero and then again increases
• b) There is no change in intensity
• c) The intensity reduces down some what and rises again
• d) The intensity is reduced down to zero and remains zero

Answer: The intensity gradually reduces to zero and then again increases

Question: For a wavelength of light ‘l’ and scattering object of size ‘a’, all wavelengths are scattered nearly equally, if

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: In Young’s double-slit experiment, if the distance between the slits is halved and the distance between the slits and the screen is doubled, the fringe width becomes

• a) Four times
• b) Eight times
• c) Double
• d) Half

Answer: Four times

Question: In a Fresnel biprism experiment, the two positions of lens give separation between the slits as 16 cm and 9 cm respectively. What is the actual distance of separation?

• a) 12 cm
• b) 12.5 cm
• c) 14 cm
• d) 13 cm

Answer: 12 cm

Question:  Colours appear on a thin soap film and on soap bubbles due to the phenomenon of

• a) Interference
• b) Dispersion
• c) Refraction
• d) Diffraction

Answer: Interference

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Two coherent monochromatic light beams of intensities I and 4I are superimposed; the maximum and minimum possible intensitites in the resulting beam are

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 0.30 mm
• b) 0.20 mm
• c) 0.53 mm
• d) 0.40 mm

Answer: 0.30 mm

Question: In an interference experiment monochromatic light is replaced by white light, we will see

• a) A few coloured bands and then uniform illumination
• b) Equally spaced white and dark bands
• c) Uniform illumination on the screen
• d) Uniform darkness on the screen

Answer: A few coloured bands and then uniform illumination

Question: In Young’s double slit experiment carried out with light of wavelength 5000 Å, the distance between the slit is 0.2 mm and the screen is at 200 cm from the plane of slits. The central maximum is at x = 0. The third maximum will be at x equal to

• a) 1.5 cm
• b) 1.67 cm
• c) 0.5 cm
• d) 5.0 cm

Answer: 1.5 cm

Question: In Young’s experiment when sodium light of wave length 5893 Å is used, then 62 fringes are seen in the field of view. Instead, if violet light of wavelength 4350 Å is used, then the number of fringes that will be seen in the field of view will be

• a) 84
• b) 74
• c) 64
• d) 54

Answer: 84

Question:  In an interference pattern by two identical slits, the intensity of central maxima is I. What will be the intensity of the same spot, if one of the slits is closed?

• a)

  

• b)

  

• c)

  

• d) None of these

Answer:

Question: If a thin mica sheet of thickness ‘t’ and refractive index ‘m’ is placed in the path of one of the waves producing interference, then the whole interference pattern shifts towards the side of the sheet by a distance

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a) 2
• b) 1
• c) 3
• d) 4

Answer: 2

Question:  A slit 5 cm wide is irradiated normally with micro waves of wavelength 1 cm. Then the angular spread of the central maximum on either side of the incident light is nearly

• a)

  

• b) 4 radian
• c) 5 radian
• d) 6 radian

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A beam of light strickes a piece of glass at an angle of incidence of 60° and the reflected beam is completely plane polarised. The refractive index of the glass is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Waves that cannot be polarised are

• a) Longitudinal waves
• b) Electromagnetic waves
• c) Transverse waves
• d) Light waves

Answer: Longitudinal waves

Question: Two polaroids are kept crossed to each other. Now one of them is rotated through an angle of 45°. The percentage of incident light now transmitted through the system is

• a) 25%
• b) 50%
• c) 75%
• d) 15%

Answer: 25%

Question:  When the angle of incidence is 60° on the surface of a glass slab, it is found that the reflected ray is completely polarised. The velocity of light in glass is

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Light of wavelength l 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 then equal to the width of the slit if D equals

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: In a Fraunhofer diffraction at a single slit of width d with incident light of wavelength 5500 Å, the first minimum is observed at angle of 30°. The first secondary maximum is observed at an angle q, equal to

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Diameter of human eye lens is 2 mm. What will be the minimum distance between two points to resolve them, which are situated at a distance of 50 m from eye. The wavelength of light is 5000 Å?

• a) 1.525 cm
• b) 12.48 cm
• c) 4.28 mm
• d) 2.32 m

Answer:  1.525 cm

Question:

• a) 2.4 mm
• b) 2.4 cm
• c) 1.2 mm
• d) 1.2 cm

Answer:  2.4 mm

Question:

• a)

  

• b)

  

• c) Zero
• d) K

Answer:

Question: In a double slit experiment, the two slits are 1 mm apart and the screen is placed 1 m away. A monochromatic light of wavelength 500 nm is used. What will be the width of each slit for obtaining ten maxima of double slit within the central maxima of single slit pattern?

• a) 0.2 mm
• b) 0.02 mm
• c) 0.1 mm
• d) 0.5 mm

Answer: 0.2 mm

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer: