JEE Physics Wave Optics MCQs Set A

Question.  Huygens' concepts of secondary wavelets
(a) Are a geometrical method to find a wavefront
(b) Allow us to find the focal length of a thin lens
(c) Give the magnifying power of a microscope
(d) Are used to determine the velocity of light

Answer: A

Question. Two waves having intensities in the ratio of 9 : 1 produce interference. The ratio of maximum to minimum intensity is equal to
(a) 4 : 1
(b) 2 : 1
(c) 9 : 1
(d) 10 : 8

Answer: A

Question. The fringe width in Young’s double-slit experiment can be increased if we decrease
(a) Separation of the slits
(b) Wavelength of the source
(c) Distance between the source and the screen
(d) All of these

Answer: A

Question. In case of Young’s experiment
(a) Both the slits get light from a single monochromatic source of light
(b) There are two virtual sources of light from same monochromatic source of light
(c) Two separate monochromatic sources of light of same wavelength are used
(d) None of these

Answer: A

Question. If light from a galaxy observed on the earth's surface has a red shift, then
(a) Galaxy is receding from the earth
(b) Galaxy is stationary w.r.t. the earth
(c) Galaxy is approaching the earth
(d) Temperature of galaxy in increasing

Answer: A

Question. In Young’s double slit experiment, the separation between the slits is halved and the distance between the slits and screen is doubled. The new fringe width is
(a) Quadrupled
(b) Doubled
(c) Halved
(d) Unchanged

Answer: A

Question.  If one of the two slits of a Young’s double slit experiment is painted over so that it transmits half the light intensity of the other then
(a) The dark fringes would be less dark and bright fringes would be less bright
(b) Bright as well as dark fringes would be more dark
(c) The bright fringes will be more bright and dark fringes will be more dark
(d) The fringe system would disappear

Answer: A

Question. Monochromatic light from a narrow slit illuminates two parallel slits producing an interference pattern on a screen. The separation between the screen and the slits is reduced to half. The fringe width
(a) Becomes half
(b) Becomes four times
(c) Is doubled
(d) Becomes one fourth

Answer: A

Question.  Two slits separated by a distance of 1mm are illuminated with red light of wavelength 6.5 × 10^–7 m. The interference fringes are observed on a screen placed 1m from the slits. The distance between the third dark fringe and the fifth bright fringe on the same side of central maxima is
(a) 1.62 mm
(b) 0.65 mm
(c) 3.25 mm
(d) 4.88 mm

Answer: A

Question. A double slit interference experiment is carried out in air and the entire arrangement is dipped in water. As a result
(a) The fringe width decreases
(b) The fringe width remains unchanged
(c) The fringe width increases
(d) Fringe pattern disappears

Answer: A

Question. In a Young’s double slit experiment the wavelength of red light is 7.8 × 10^–5 cm and that of blue light is 5.2 × 10^–5 cm. The value of n for which (n + 1)th blue bright band coincides with nth bright red band is
(a) 2
(b) 1
(c) 3
(d) 4

Answer: A

Question.  In Young’s double-slit experiment, a glass plate of refractive index 1.5 and thickness 5 × 10^–4 cm is kept in the path of one of the light rays. Then
(a) The optical path of the ray will increase by 2.5 × 10^–4 cm
(b) The fringe width will decrease
(c) The fringe width will increase
(d) There will be no shift in the interference pattern

Answer: A

Question. Which of the following is correct regarding microscope and telescope?
(a) Telescope provides resolution whereas microscope provides magnification
(b) Telescope provides magnification, whereas microscope provides resolution
(c) Both provide resolution
(d) Both provide magnification

Answer: A

Question. If Young’s experiment is performed using two separate identical sources of light instead of using two slits and one light source then the
(a) Fringes will not be obtained
(b) Contrast between bright and dark fringes increases
(c) Interference fringes will be brighter
(d) Interference fringes will be darker

Answer: A

Question. Oil floating on water looks coloured due to interference of light. What should be the order of magnitude of the thickness of oil layer in order that this effect may be observed?
(a) 10^–6 m
(b) 10^–2 m
(c) 10^–10 m
(d) 10^–8 m

Answer: A

Question.  When white light is incident normally on an oil film of thickness 10^–4 cm and refractive index 1.4 then the wavelength which will not be seen in the reflected system of light is
(a) All of these
(b) 4000 Å
(c) 5600 Å
(d) 7000 Å

Answer: A

Question. Imperfections in optical lenses can be observed with the help of
(a) Newton's Rings
(b) Lloyd's single miror experiment
(c) Fresnel's Biprism
(d) Young's double slit experiment

Answer: A

Question.  Dark and colour patterns on thin soap films are due to
(a) Interference of light
(b) Diffraction of light
(c) Dispersion of light
(d) Polarization of light

Answer: A

Question. Choose the correct statement
(a) All of these
(b) Glass lenses used in cameras and other optical instruments are usually coated with a transparent thin film, such as magnesium fluoride (MgF₂) to reduce or eliminate unwanted reflection
(c) Solar cells are often coated with a transparent thin film, such as silicon monoxide (SiO) to minimize reflective losses
(d) While watching television by means of an antenna, a passing nearby aeroplane can produce wavering ghost images in the television picture

Answer: A

Question.  The beautiful iridescent (like a rainbow) colors on the wings of a tropical or morpho butterfly are due to
(a) Thin film interference of light
(b) Polarization of light
(c) Diffraction of light
(d) Dispersion of light

Answer: A

Question. Some currency notes (to avoid counterfeits) change their colour as you tilt them. This is due to
(a) Interference
(b) Refraction
(c) Diffraction
(d) Polarization

Answer: A

Question. Rainbows are classic example of the phenomenon of
(a) Interference
(b) Diffraction
(c) Polarization
(d) Absorption

Answer: A

Question. The phenomenon of diffraction can be exhibited by
(a) All of these
(b) X-rays
(c) Microwaves
(d) Infrared waves

Answer: A

Question. Though quantum theory of light can explain a number of phenomenon observed with light, it is necessary to retain the wave nature of light to explain the phenomenon of
(a) Diffraction
(b) Photoelectric effect
(c) Compton effect
(d) Black body radiation

Answer: A

Question.  A diffraction pattern is obtained using a beam of red light. What happens, if the red light is replaced by blue light?
(a) Diffraction bands become narrower and get crowded together
(b) No change
(c) Bands become broader and farther apart
(d) Bands disappear

Answer: A

Question. The main difference in the phenomenon of interference and diffraction in light waves is that
(a) Diffraction is due to interaction of light from same wavefront, whereas the interference is the interaction of two waves derived from the same source
(b) Diffraction is due to interaction of light from the same wave-front whereas interference is the interaction of waves from two isolated sources
(c) Diffraction is due to interaction of waves derived from the same source, whereas the interference is the bending of light from the same wavefront
(d) Diffraction is caused by reflected waves from a source whereas interference is caused due to refraction of waves from a surface

Answer: A

Question.  The condition for observing Fraunhofer diffraction from a single slit is that the wave front incident on the slit should be
(a) Plane
(b) Elliptical
(c) Cylindrical
(d) Spherical

Answer: A

Question. A parallel beam of monochromatic light of wavelength 5000 Å is incident normally on a single narrow slit of width 0.001 mm. The light is focussed by a convex lens on a screen placed on focal plane. The first minimum will be formed for the angle of diffraction equal to
(a) 30°
(b) 50°
(c) 15°
(d) 0°

Answer: A

Question. Monochromatic light of wavelength 580 nm is incident on a slit of width 0.30 mm. The screen is 2m from the slit. The width of the central maximum is
(a) 7.7 × 10^–3 m
(b) 6.20 × 10^–3 m
(c) 2.25 × 10^–3 m
(d) 3.35 × 10^–3 m

Answer: A

Question.  The resolving power of a compound microscope will be maximum when
(a) Violet light is used to illuminate the object instead of red light
(b) Red light is used to illuminate the object
(c) Infra red light is used to illuminate the object instead of visible light
(d) The microscope is in normal adjustment

Answer: A

Question. Why a DVD stores almost 30 times more information than a CD?
(a) DVD uses shorter - wavelength lasers of 6350Å but CD uses an infrared laser of 7800 Å
(b) CD uses shorter wavelength laser compared to a DVD
(c) CD works on the principle of diffraction
(d) DVD works on diffraction of light

Answer: A

Question. If a classroom door is open just a small amount, we can hear sounds coming from the room but we can't seewhat is going on inside the room because
(a) Diffraction of sound is easier as its wavelength is large
(b) Diffraction of light is easier as its wavelength is small
(c) Sound waves can be polarizedLight waves can be polarized
(d) Light waves can be polarized

Answer: A

Question. When you look at a clear blue sky you see tiny specks and hair like structures floating in your view, called "floaters". This is basically
(a) Diffraction pattern
(b) Interference pattern
(c) Emission spectra
(d) Absorption spectra

Answer: A

Question. Light wave travel in vacuum along the x-axis, which of the following may represent the wave front
(a) x = a
(b) y = a
(c) z = a
(d) x + y + z = a

Answer: A

Question. In Young double slit experiment, 12 fringes are obtained in a certain fragment of the screen, when light of wavelength 600 nm is used. If the wavelength of light is changed to 400 nm, number of fringes observed in the same segment of the screen is
(a) 18
(b) 12
(c) 24
(d) 30

Answer: A

Question. Two points separated by 0.05 mm can just be inspected in a microscope when light of wavelength 6000 Å is used. If light of wavelength 3000 Å is used then the limit of resolution becomes
(a) 0.025 mm
(b) 0.1 mm
(c) 0.15 mm
(d) 0.05 mm

Answer: A

Question. In Young's double slit experiment, the distance between the slits is reduced to half and the distance between the slit and the screen is doubled, then fringe width
(a) Will become four times
(b) Will be doubled
(c) Will become half
(d) Will not change

Answer: A

Question. In Young's experiment, the separation between 5th maxima and 3rd minima is how many times as that of fringe width?
(a) 2.5 times
(b) 2 times
(c) 3 times
(d) 5 times

Answer: A

Question.  Refractive index of material is equal to the tangent of polarising angle. It is called
(a) Brewster's law
(b) Lambert's law
(c) Malus' law
(d) Bragg's law

Answer: A

Question. If the amplitude ratio of two sources producing interference is 3 : 5, the ratio of intensities of maxima and minima is
(a) 16 : 1
(b) 5 : 3
(c) 25 : 16
(d) 25 : 9

Answer: A

Question.  In a Young's double slit experiment, the source illuminating the slits is changed from blue to violet. The width of the fringes
(a) Decreases
(b) Increases
(c) Becomes unequal
(d) Remains same

Answer: A