Multiple Choice Questions
UNIT I
Q.1 )
Interference is due to superposition of ---------------- waves
a)Two
b)Three
c)four
d)any number of
(d)
Q.2) When light traveling in air gets reflected from water surface, there is ----------a) phase change of π
b) phase change of π/2
c)phase change of π/4
d) no phase change
(a)
Q.3) For light of wavelength 6000 o A , which of the following path difference will give
constructive interference ?
a) 0.1 μm
b) 0.3 μm
c)0.6 μm
d)0.5 μm
(c)
Q.4) If light travels a distance of 3 mm in a medium of refractive index 1.5 ,
the equivalent distance travelled in air will be ------ mm
a) 2
b) 4.5
c) 1.5
d) 0
Q.5) For consecutive interference , the path difference is ---------a) nλ
b) (2n-1)λ/2
c) (2n-1) π
d) 2nπ
(a)
Q.6) Interference is destructive if path difference is ---------------a) nλ
b) (2n-1)λ/2
c) (2n-1) π
d)2nπ
(b)
Q.7) For constructive interference ,the phase difference is-----------a) (2m-1)π
b) 2mπ
c)mλ
d)(2m-1)λ/2
(b)
Q.8) Phase difference of 2π corresponds to a path difference of --------a) λ/2
b) λ
c) λ/4
d) 3λ/2
(b)
Q.9) When light travels from water to air, the reflected wave undergoes-----------a) phase change of π
b) phase change of π/2
c) phase change of π/4
d)no phase change
(d)
Q.10) When a light wave travels distance d in a medium of refractive Index µ,the equivalent
distance traveled in air is-------------a) d / µ
b) µd
c) d
d) µ/d
(b)
Q.11) Light travelling from a medium of refractive index √3 into air is incident on the interface
at an angle of 30 0 .The angle of refraction will be --------a) 600
b) 300
c) 450
d) 900
(a)
Q.12) When a soap film is illuminated with white light from a point source, ---------will be seen .
a) coloured fringes
b) no fringes
c) yellow fringes
d) uniform illumination
(a)
Q.13) If wavelength of light incident on a wedge shaped film is increased, the fringe width --------a) increases
b) decreases
c) remain same
d)first increases and then decreases
(a)
Q.14) If a refractive index of the medium of a wedge shaped film increases ,fringe width -------a) increases
b) decreases
c) remains same
d) first increases and then decreases
(b)
Q.15) If air film in Newton's rings experiment is replaced with another medium of larger refractive
index, the diameter of bright rings ------a) increases
b) decreases
c) remains same
d)first increases and then decreases
(b)
Q.16) Antireflection coatings reduce intensity of reflected light by-------a) absorption
b) destructive interference
c) constructive interference
d)scattering
(b)
Q.17)Optical flatness of surfaces is tested using interference in -----------a) uniform thickness film
b) wedge shaped film
c) both a) and b)
d)none of above
(b)
Q.18) The centre of Newtons rings in transmitted light is --------a) bright
b) dark
c) dependent on wavelength
d)dependent on radius of curvature of plano-convex lens.
(a)
Q.19) If the thickness of the glass plate on which lens is kept in Newton's rings experiment is
increased ,the diameters of rings will ---------a) increase
b) decrease
c) remain same
d) none of above
(c)
Q.20) In Newton's rings experiment diameters of bright rings are proportional to ------a) λ
b)1/ λ
c) √λ
d) 1/√λ
(c)
Q.21) In a fraunhofer diffraction at a single slit of width 2 μm, illuminated with monochromatic
light of wavelength 5000 oA , the total number of minima is ------a) 10
b) 5
c)4
d) 8
(d)
Q.22) A line on a diffraction grating is ---------a) an opaque space
b) a slit
c) a slit and an opaque space
d)none of above
(c)
Q.23) The condition for minimum intensity in a diffraction grating is ----------a) a sinɵ = nλ
b) (a+b) sin ɵ = nλ
c) a sinɵ = ( n + 1/2) λ
d)(a+b) sin ɵ = (n/N )λ
(d)
Q.24)If the width of each slit is twice the width of each opaque space in a diffraction grating , the
principal maximum of order---------- will be absent in its diffraction pattern.
a) 1
b) 2
c) 3
d) 4
(c)
Q.25) A diffraction grating contains 10,000 lines. There will be ---------- minima between two
adjucent principal maxima in its diffraction pattern .
a) 10,000
b) 9,999
c) 9,998
d)10,001
(b)
Q.26) The central fringe in diffraction pattern is always
a) bright
b) dark
c) difficult to say
d) None of these
(a)
Q.27) Calculate the angle at which first order minima appears for a single slit of width 0.1 mm and
wavelength of light is 5890 0 A
a) 0.33 deg
b) 0.40 deg
c)0.30 deg
d) 0.50 deg
(a)
Q.28) Type of diffraction is used mostly for Industrial applications---------------------a) Fraunhofer
b) Fresnel
c) Both (a) and (b)
d)Either (a) or (b)
Q.29) The central fringe in diffraction pattern is always. -------------------a) bright
b) dark
c) difficult to say
d)None of these
(a)
Q.30) A grating is able to resolve two very close spectral lines of wavelength 58900A and 5896 0A
in its first order diffraction. The resolving power of the grating is ------a) close to 6000
b) close to 1000
c) close to 3000
d) close to 12,000
(b)
Q.31) When white light is incident on a diffraction grating , the light diffracted more will be
a) blue
b) yellow
c) violet
d) red
(d)
Q.32) A parallel beam of light wavelength 600nm gets diffracted by a single slit of width 0.2 mm
The angular divergence of the first maxima of diffracted light is ------------------a) 6.3 x 10-3 rad
b) 3 x 10 -3 rad
c)4.5 x 10-2 rad
d)9 x 10-2 rad
(c)
Q.33 ) In Fraunhofer diffraction the wavefront undergoing diffraction has to be ---------a) Spherical
b)cylindrical
c) elliptical
d) plane
(d)
Q.34 ) In a single slit diffraction, the first diffraction minima is observed of an angle of 30 0 ,When
the light of wavelength 500 mm is used. The width of the slit is ------------a) 5 x 10-5 cm
b) 2.5 x 10-5 cm
c) 10 x 10-5 cm
d) 1.25 x 10-5 cm
(c)
Q.35) If 1000 is the resolving power of a grating in the first order,its resolving power in second
order is given by --------a) 500
b) 1000
c) 2000
d) none of these
(c)
Q.36) In the diffraction pattern due to a single slit, the width of the central maximum ,
(a) With red light is less than with violet light
(b) with red light is more than with violet light
(c) with red light is equal to with violet light
(d) none of these
(b)
Q.37) Consider Fraunhofer diffraction pattern obtained with a single slit at normal incidence. At the
angular position of the first diffraction minimum , the phase difference in radians between
the wavelets from the opposite edges of the slit is --------------a) π/4
b) π/2
c) 2π
d)π
(d)
Q.38) A grating which would be more suitable for constructing a spectrometer for the visible and
ultraviolet regions,should have ------a) 100 lines/cm
b) 1000 lines/cm
c) 10,000 lines / cm
d) 106 lines /cm
(c)
Q.39)Which of the following orders of maxima cannot be absent in the diffraction pattern of any
grating ?
a) 0
b) 1
c) 2
d)0 and 1
(d)
Q.40) In the diffraction pattern produced by a grating having N lines, there will be -----------secondary maxima between adjacent principal maxima.
a) N-1
b) N-2
c) N
d) N+ 1
(b)
Q.41) For particles of very small size ,the intensity of scattered light is ---------------a) directly proportional to wavelength
b) inversely proportional to wavelength
c) inversely proportional to fourth power of wavelength
d)directly proportional to fourth power of wavelength
(c)
Q.42) Intensity of second secondary maximum is ----- % of the intensity of central maximum in
Fraunhofer diffraction at a single slit
a) 16.2
b) 0.8
c) 4.5
d) 1.62
(d)
Q.43) In Fraunhofer diffraction at a single slit of width a, illuminated with monochromatic light of
wavelength λ, the maximum number of minima on one side of the central maximum is ----a) a / λ
b) 2a / λ
c) a /2 λ
d)λ / a
(b)
Q.44) If a is width of each slit , b is width of each opaque space and W is the width of a diffraction
grating , the width of a line is ------a) a
b) b
c) W
d)a + b
(d)
Q.45) The Newton's rings are formed due to the phenomenon of -----------------a) interference in thin film
b) diffraction
c)interference due to pin holes
d) diffraction due to circular aperture
Q.46) When light wave is reflected at the interface between air and glass the reflected ray changes
phase by ---a) o
b) π/2
c) π
d) 2π
Q.47) A transparent substance having uneven surface is kept in contact with another flat surface in
such a way that they form a wedge shape. When illuminated by monochromatic light,it will
give fringes of ---------a) equal thickness
b) different thickness
c) cannot be predicted
d)depend on type of glass material
Q.48) In interference experiment , monochromatic light is replaced by white light we will see ------a)uniform illumination of screen
b) uniform darkness on the screen
c) equally spaced dark and white bands
d)few coloured bands and then general illumination
Q.49) What is the nature of interference pattern for thin film of wedge shaped ?
a) concave outside
b) convex outside
c) equally spaced
d)concave inside
Q.50) In a newton's rings experiment the diameter of 10th dark ring is found to be 0.433 cm .The
radius of curvature of planoconvex lens is 70 cm . What is the wavelength of light used ?
a) 6696Ao
b) 6769Ao
c) 6596Ao
d) 6896 Ao
Q.45 ) In the diffraction pattern produced by a grating having N lines, there will be -------------secondary maxima between adjacent principal maxima.
a) N-1
b) N-2
c) N
d) N +1
(b)
Dr Supriya Upasani
Associate Professor
Engineering Physics