In the print window choose “Save as PDF”. The file prints without a web address or date line.
Mere Teacher · Previous Year Questions
NEET Physics · Wave Optics · Set 3 (Q61-90)
Scan or visit mereteacher.com for free PYQ practice, timed CBT tests, step-by-step solutions and BroBot AI. Answers and solutions are free with a sign-up.
61.
Two slits separated by a distance of 1mm are illuminated with light of wavelength 6.5×10−7m. The interference fringes are observed on a screen placed at 1m from the slits. The distance between the third dark fringe and the fifth bright fringe is equal to
(1)0.655mm
(2)1.625mm
(3)3.125mm
(4)4.785mm
62.
The polarising angle for transparent medium is θ, v is the speed of light in that medium. Then the relation between θ and v is ( c= velocity of light in air)
(1)θ=tan−1(cv)
(2)θ=cot−1(cv)
(3)θ=sin−1(cv)
(4)θ=cos−1(cv)
63.
Diameter of the objective of a telescope is 200cm. What is the resolving power of a telescope? Take wavelength of light =5000A.
(1)1×106
(2)6.56×106
(3)3.28×106
(4)3.28×105
64.
Light of wavelength 600nm is incident normally on a slit of width 0.2mm. The angular width of central maxima in the diffraction pattern is (measured from minimum to minimum)
(1)6×10−3rad
(2)4×10−3rad
(3)2.4×10−3rad
(4)4.5×10−3rad
65.
Wave front is the locus of all points, where the particles of the medium vibrate with the same
(1)phase
(2)amplitude
(3)frequency
(4)period
66.
In a Young's double slit experiment, light of 500nm is used to produce an interference pattern. When the distance between the slits is 0.05mm, the angular width (in degree) of the fringes formed on the distance screen is close to
(1)0.17∘
(2)1.7∘
(3)0.57o
(4)0.07o
67.
With the help of a telescope that has an objective of diameter 200cm, it is proved that light of wavelengths of the order of 6400Å coming from a star can be easily resolved. Then, the limit of resolution is
(1)39×10−8deg
(2)39×10−8rad
(3)19.5×10−8rad
(4)19.5×10−8deg
68.
Two wavelengths of sodium light 590nm and 596nm are used one after another to study diffraction due to single slit of aperture 2×10−6m. The distance between the slit and the screen is 1.5m. The separation between the position of first maximum of the diffraction pattern obtained in the two cases is
(1)5.5mm
(2)5.75mm
(3)6.25mm
(4)6.75mm
69.
In Young's double slit experiment for what order does the wavelength of red light (λ=780nm) coincide with (m+1)th order of blue light (λ=520nm)
(1)1
(2)2
(3)3
(4)4
70.
A monochromatic light of frequency 5×1014Hz travelling through air, is incident on a medium of refractive index ' 2 '. Wavelength of the refracted light will be:
(1)400 nm
(2)300 nm
(3)600 nm
(4)500 nm
71.
Two coherent sources of intensity ratio 9:4 produce interference. The intensity ratio of maxima and minima of the interference pattern is
(1)13:6
(2)5:1
(3)25:1
(4)3:2
72.
The wavelength of the light used in Young's double slit experiment is λ. The intensity at a point on the screen where the path difference is λ/6 is I. If I0 denotes the maximum intensity, then the ratio of I and I0 is
(1)0.866
(2)0.5
(3)0.707
(4)0.75
73.
In a double-slit experiment, at a certain point on the screen the path difference between the two interfering waves is 1/8 of a wavelength. The ratio of the intensity of light at that point to that at the centre of a bright fringe is
(1)0.853
(2)0.533
(3)0.234
(4)0.123
74.
The speed of electrons in a scanning electron microscope is 1×107ms−1. If the protons having the samespeed are used instead of electrons, then the resolving power of scanning proton microscope will be changedby a factor of:
(1)1837
(2)18371
(3)1837
(4)18371
75.
The optical path difference between two identical light waves arriving at a point is 31.5λ where ' λ ' is the wavelength of light used. The point is [Two light sources are coherent]
(1)neither bright nor dark
(2)dark
(3)bright
(4)alternatively bright and dark.
76.
The path difference between two interfering light waves meeting at a point on the screen is (287)λ. The band obtained at that point is
(1)87th dark band
(2)44th dark band
(3)44th bright band
(4)87th bright band
77.
The head lights of a jeep are 1.2m apart. If the pupil of the eye of an observer has a diameter of 2mm and light of wavelength 5896Å is used, what should be the maximum distance of the jeep from the observer if the two head lights are just separated?
(1)33.9km
(2)33.9m
(3)3.39km
(4)3.39m
78.
When Young's double slit experiment is performed in air, the Y-coordinates of central maxima and 10th maxima are 2cm and 5cm respectively. If the apparatus is immersed in a liquid of refractive index 1.5, the corresponding Y-coordinates will be
(1)2cm,7.5cm
(2)3cm,6cm
(3)2cm,4cm
(4)34cm,310cm
79.
Blue light travelling in vacuum has a wavelength of 450nm. It enters a medium whose refractive index is 1.5 . What is its frequency in the medium? (Speed of light in vacuum =3×108m/s )
(1)6.67×1014Hz
(2)1015Hz
(3)−4.45×1014Hz
(4)1014Hz
80.
An unpolarised light is incident at an interface of two dielectric media having refractive indices of 2 (incident medium) and 23 (medium) respectively. To satisfy the condition that reflected and refracted rays are perpendicular to each other, the angle of incidence is ____ .
(1)45∘
(2)60∘
(3)10∘
(4)30∘
81.
When the same monochromatic ray of light travels through glass slab and through water, the number of waves in glass slab of thickness 6cm is same as in water column of height 7cm. If refractive index of glass is 1.5 then refractive index of water is
(1)1.258
(2)1.269
(3)1.286
(4)1.310
82.
Two sources are said to be coherent if they produce waves
(1)having a constant phase difference
(2)of equal wavelength
(3)of equal speed
(4)having same shape of wave front.
83.
In a Young's double slit experiment, the path difference, at a certain point on the screen, betwen two interfering waves is 81thof wavelength. The ratio of the intensity at this point to that at the centre of a bright fringe is close to:
(1)0.74
(2)0.85
(3)0.94
(4)0.80
84.
In Young's double slit arrangement, slits are separated by a gap of 0.5mm, and the screen is placed at adistance of 0.5m from them. The distance between the first and the third bright fringe formed when the slitsare illuminated by a monochromatic light of 5890∖AAis :-
(1)1178×10−9m
(2)1178×10−6m
(3)1178×10−12m
(4)5890×10−7m
85.
Consider the diffraction pattern obtained from the sunlight incident on a pinhole of diameter 0.1μm. If thediameter of the pinhole is slightly increased, it will affect the diffraction pattern such that:
(1)its size decreases, but intensity increases
(2)its size increases, but intensity decreases
(3)its size increases, and intensity increases
(4)its size decreases, and intensity decreases
86.
Due to Doppler's effect, the shift in wavelength observed is 0.1Å for a star producing wavelength 6000Å. Velocity of recession of the star will be
(1)5kms−1
(2)25kms−1
(3)20kms−1
(4)10kms−1
87.
The central fringe in the interference pattern obtained in Young's double slit experiment will be a dark fringe when the phase difference between the waves from the two slits is
(1)zero
(2)2π
(3)π
(4)3π
88.
A polarizer - analyzer set is adjusted such that the intensity of light coming out of the analyzer is just 10% of the original intensity. Assuming that the polarizer-analyzer set does not absorb any light, the angle by which the analyzer need to be rotated further to reduce the output intensity to be zero is:
(1)60o
(2)18.4o
(3)45o
(4)71.6o
89.
Young's double slit inteference apparatus is immersed in a liquid of refractive index 1.44. It has slit separation of 1.5 mm. The slits are illuminated by a parallel beam of light whose wavelength in air is 690 nm. The fringe width on a screen placed behind the plane of slits at a distance of 0.72 m, will be:
(1)0.23 mm
(2)0.33 mm
(3)0.63 mm
(4)0.46 mm
90.
A microwave of wavelength 2.0cm falls normally on a slit of width 4.0cm. The angular spread of the central maxima of the diffraction pattern obtained on a screen 1.5m away from the slit, will be:
