Wave Optics Questions and Answers

20 A light wave is incident normally over a slit of width 24 x 10 5 cm The angular position of second dark fringe from the central maxima is 30 What is the wavelength of light 6000 3 3000 2 5000 4 1500

Consider Fraunhofer diffraction pattern obtained with a single slit illuminated 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 1 T 2 2 3 4 4 2

Young s double slit experiment is conducted in a liquid of refractive index u as shown in figure A thin transparent slab of refractive index is placed in front of the slit S If H 4 t 8 m the magnitude of optical path difference wrt liquid at O in um is 3 2 3 liquid monocromatic beamlight S S liquid D S S d D O so so

A photon of frequency v strikes an electron of mass m initially at rest After scattering at an angle the photon loses half of its energy If the electron recoils at an angle 0 which of the following is are true sine A The ratio of the magnitudes of momenta of the recoiled electron and scattered photon is sino B Change in photon wavelength is hc C The ratio of the magnitudes of momenta of the recoiled electron and scattered photon is sino sine hc D Change in photon wavelength is 2v

A single slit of width a is illuminated with a monochromatic light of wavelength 2 The angular width of the central maximum is found to be 0 If the slit width is halved and the diffraction is observed using light of same wavelength the width of a secondary maximum will be A 200 B 0 C D 0 2 00 4

In a Davisson Germer experiment Helium atoms were used in place of electrons What should be the energy of Helium so that a strong peak of scattered He appears at an angle of 500 as was the case with electrons having an energy of 54 eV Take mass of He atoms to be 7500 times the mass of electrons A 7 2 meV B 3 6 meV C 405 MeV D 202 5 MeV

2 A person AB of height 170 cm is standing in front of a vertical plane mirror His eyes are at height 164 cm from ground At what distance from P should a hole be made in the mirror so that he cannot see the top of his head A a 167 cm c 163 cm B P b 161 cm d None of these th

Pure blue and red light beams are passing through a glass prism Which of the following is tru A Blue light has higher dispersive power B Blue light has higher refractive index C Blue light has less refractive index D Refractive index is equal for both blue and red lights

2 The intensity of the polarized light becomes 1 th of its initial value after passing through the 20 analyser Angle between the transmission axis of the analyser and the initial direction of electric field of polarized light is 1 sin 1 3 cos 1 2 5 1 2 5 2 5 4 tan 2 5 2 cos

A telescope has an objective lens of 20 cm diameter and is situated at a distance of 2 km from two objects The minimum distance between the two objects which can be resolved by the telescope when mean wavelength of light is 6000 is order of 1 7 m 3 7 mm 2 7 cm 4 7 km

38 A student does the experiment on tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence He can get a correct measure of the angles of incidence and angle of emergence by following the labelling indicated in figure 1 3 4

Refrerring to the figure the image of the quadrilateral XYZW placed front of the concave mirror M 15cm B C F C W X 3cm will be congruent of itself will be similar to itself will neither be congruent nor be similar

A double slit experiment is performed with a slit separation of 1 mm It is found that the central diffraction maximum contains exactly 13 bright interference fringes The first diffraction minimum eliminates a bright fringe as it occurs at the same location as that of a bright fringe The number of bright fringes that lie between the first and the second minima of the envelope is A 6 B 7 C 13

Waves originating from three coherent monochromatic sources reach a point O with identical polarization amplitude and phase The resultant intensity at that point is 1 The second source suddenly develops a steady additional phase of with respect to the first source The third source continues as before The intensity at O will be modified to A I B C D 8 3 Io 4 Io

A beam of light with a plane wavefront needs to be transformed into one with a convergent spherical wavefront For this purpose which of the following may be suitable A a double slit B a totally reflecting prism C a concave lens or a convex mirror d ncave mirror or a convex lens

A point source S is placed at a distance of 15 cm from a converging lens of focal length 10 cm on its principal axis Where should a diverging mirror of focal length 12 cm be placed so that a real image is formed on the source itself a 6 cm to the left of the lens b 6 cm to the right of the lens c 10 cm to the left of the lens d 10 cm to the right of the lens

Phy Section B This section contains 15 SINGLE CORRECT TYP questions Out of these 15 questions candidate Read More ntensity at the centre of the screen in YDSE is 8 0 If ne of the slits is covered then intensity at centre wil e O 410 O 210 0

A compound microscope is designed to resolve objects which are 0 01 mm apart If the focal length of the objective is 4 cm and the wavelength of the light used is 550 nm then the diameter of the objective is A 0 27 mm B 0 54 mm C 2 7 mm D 54mm

In a double slit experiment the slit separation is 0 16 mm and the width of each slit is 0 02 mm The slits are illuminated with light of certain wavelength and the resulting interference pattern is viewed on a screen 2m away How many bright fringes are there in the central diffraction maximum A 17 B 16 C 15 D cannot be determined without knowledge of the wavelength of light

Two thin plano convex lenses each of focal length m in air are placed at some distance d from each other as shown in the figure The space between the lenses are filled with a substance with refractive index The distance d between the lenses are so adjusted that a parallel beam of light passes through such an optical system remains parallel Take refractive index of lens Choose correct option A B If 4 1 2 d 90 cm d 100 cm H air

In Young s double slit experiment a glass plate is placed before a slit which absorbs half the intensity of light Under this case a The brightness of fringes decreases b The fringe width decreases c No fringes will be observed d The bright fringes become fainter and the dark fringes have finite light intensity

30 A transparent rectangular slab of length 1 20 cm and thickness d cm is placed in front of a converging lens of focal length f 20 cm screen S is placed in the focal plane of the lens Refractive index of material of the slab increases linearly from 40 1 5 at the bottom f by an amount du 2 0 x 10 4 between the bottom and the top faces parallel beam is made to incident on the slab as shown in the figu What kind of light pattern appears on the screen

129 In given diagram calculate value of x for which intensity at point P is equal to intensity at point O S and S are coherent sources AD S 22 D S 1 3D 3 2D ortions of X Screen 2 2D 4 3D X 129 L fas 16 05 0 Cogl 1 3

0 Monochromatic light of wavelength 620 nm passes through a very narrow slit S and then strikes a screen in which are two parallel slits S and S as in Figure P37 70 Slit S is directly in line with S and at a distance of L 1 20 m away from S whereas S is displaced a distance d to one side The light is detected at point P on a second screen equidistant from S and S When either one of the slits S and S is open equal light intensities are measured at point P When both are open the intensity is three times larger Find the minimum possible value for the slit separation d S S DS d Sq I P

Interference fringes are produced using Lloyd s mirror and a 606 nm source as shown in Figure 37 15 Fringes 1 20 mm apart are formed on a screen 2 00 m from the real source S Find the vertical distance of the source above the reflecting surface

3 sin 2 4 2 sin 2 White light is incident normally on a glass plate placed in air If the thickness of glass plate is 5000 and its refractive index is 3 2 then among the following wavelength that is strongly reflected by the plates will be Visible light range is 4000 to 7000 1 4700 A 3 5500 A 2 6000 4 6500

DOPPLER S EFFECT sees traffic jam A speeding motorcyclist ahead him He slows down to 36 km hour He finds that traffic has eased and a car moving ahead of him at 18 km hour is honking at a frequency of 1392 Hz If the speed of sound is 343 m frequency of the honk as heard by him will b 1372 Hz a 1332 Hz c 1412 Hz d 1454 Hz CE

A diffraction grating with 10 lines m is used to determine the wavelength of source The angle of first order diffraction is 30 The wavelength of th monochromatic source is 6 1000 nm c 400 nm b 500 nm d 600 nm

ANGLE OF DEVIATION REFRACTIVE INDEX A thin prism of angle 15 made of glass of refractive index 1 5 is combined with another prism of glass of refractive index u 1 75 The combination c 10 of the prisms produces dispersion without devi The angle of the second prism should be b 7 a 5 d 1 Desktop Dans

In Michelson interferometer arrangement if one of the mirrors is moved by a distance 0 08 mm if the wavelength of the incident light is 6400 find the number of fringes which will cross the field of view

sing the expression 2d sin 0 2 one calculates the values of d by measuring the corresponding angles 0 in the range to 90 The wavelength is exactly known and the error in 0 is constant for all values of 0 As 0 increases from 0 A The absolute error in d remains constant 3 The absolute error in d increases C The fractional error in d remains constant D The fractional error in d decreases

Q14 When a thin plate of refractive index 1 5 is placed in the path of one of interfering beams of Michelson Interferometer a shift of 30 fringes is observed If the thickness of plate is 0 018 mm the wavelength of the used light is

The refractive index of a medium is 3 If the unpolarised light is incident on it from air at the polarizing angle of the medium the angle of refraction is NCERT Pg 379 1 60 2 45 3 30 4 0 17 When interference of light waves takes place NCERT Pg 361 1 Energy is created in the region of maximum intensity 2 Energy is destroyed in the region of minimum intensity 3 Conservation of energy hold good and energy is redistributed 4 Conservation of energy does not hold good Two points separated by a distance of 0 1 mm can just be inspected in a microscope when light of wave length 6000 is used If the light of wavelength of 8000 A is used then the limit of resolution will be NCERT Pg 373 1 0 8 mm 2 1 2 mm 3 0 1 mm 4 0 13 mm 19 Transverse nature of light was confirmed by NCERT Pg 376 the phenomena of 1 Reflection of light 2 Diffraction of light 3 Interference of light 4 Polarisation of light A light of wavelength 550 nm coming from a distant star The limit of resolution of a telescope whose objective has a diameter of 2 mis NCERT Pg 373 20 1 3 38 x 10 7 rad 2 3 35 x 10 5 rad 3 3 35 x 10 6 rad 4 2 15 x 10 7 rad

Two broad monochromatic beams A and B of plane coherent waves of the same intensity and wavelength propagating at angle 0 from each other Simultaneously illuminate a cylindrical screen Direction of propagation of both beams are perpendicular to the axis of the screen Consider a point P on the screen at angular position from the line of propagation of the beam A as shown in figure Find distance between adjacent interference fringes on the screen near the point P Assume that the distance between adjacent fringes is much less than the radius of the cylinder A C 2 2 cos sin 2 sin 0 sin 70 2 B 2 0 2sin 2 cos 0 P D 2 sin 0 sin0

81 plane polarised and unpolarised light falls normally on a polarising sheet On rotating the polarising sheet about the direction of the incident beam the transmitted intensity varies by a factor 4 The ratio of intensities I and I respectively of the polarised and unpolarised components in the incident beam is 5 1 27 3 3 5

An arrangement for YDSE is shown in figure S is a light source then find the position of central maxima from point O on screen B f 20 cm S 1 mm 20 cm Options 5 mm below O 10 0 80 cm 1m Screen A 5 mm above O 30 mm below O 3 mm O Screen B k

The slits in Young s double slit experiment are illuminated by light of wavelength 6000 A If the path difference at the central bright fringe is zero then the path difference at fourth bright fringe is NCERT Pg 364 1 2 4 x 10 6 m 2 1 2 x 10 6 m 3 10 6 m 4 0 5 x 10 6 m

7 A beam of light of 600 nm from a distant source falls on a single slit 1 mm wide and the resulting diffraction pattern is observed on a screen 2 m away The distance between first dark fringes on either side of the central bright fringe is AIPMT 2014 1 1 2 cm 2 1 2 mm 3 2 4 cm 4 2 4 mm

2 The intensity at the maximum in a Young s double is lo Distance between two slits is is the wavelength of light used in the experiment What will be the intensity in front of one of the slits on the screen placed at a distance D 10 d NEET 2016 1 1 2 slit experiment d 5 where 2

Angular width of the central maxima in the Fraunhofer diffraction for 6000 is 0 When the same slit is illuminated by another monochromatic light the angular width decreases by 30 The wavelength of this light is NEET 2019 Odisha 2 1800 A 6000 1 420 A 121 1300 1

Q46 In Young s double slit experiment the source is red light of wavelength 7 x 10 7 m When a thin glass plate of refractive index 1 5 at this wavelength is put in the path of one of the interfering beams the central bright fringe shifts by 10 3 m to the position previously occupied by the 5th bright fringe Find the thickness of the plate When the source is now changed to green light of wavelength 5 10 7 m the central fringe shifts to a position initially occupied by the 6th bright fringe due to red light Find the refractive index of glass for green light Also estimate the change in fringe width due to the change in wavelength 1997

Q40 A point source Semitting light of wavelength 600 nm is placed at a very small height h above a flat reflecting surface AB see figure The intensity of the reflected light is 36 of the incident intensity Interfer ence fringes are observed on a screen placed parallel to the reflecting surface at a very large distance D from it 2002 A h P S Screen B D a What is the shape of the interference fringes on the screen b Calculate the ratio of the minimum to the maxi mum intensities in the interference fringes formed near the point P shown in the figure c If the intensity at point P corresponds to a max imum calculate the minimum distance through which the reflecting surface AR should be shifted so

Two source s1 s2 are separate by distance 4 2lemda if an observer stand in middle of t he two observer start moving towards s2 F und distance travelled by observer when he meet minima for second time

In the figure shown S and S are effective point sources of radiation excited by the same oscillator They are coherent and in phase with each other Placed 4 0 m apart along the y axis they emit equal amounts of power in the form of electromagnetic waves of wavelength 1 0 m A detector is moved along S x At which of the following distances from S does the detector receive a minimum signal y A 0 54 m B 1 16 m C 3m S S 4 m X

Consider the standard Young s double slit experiment setup Let Ax represent the path difference between the waves reaching P Mark the incorrect statement d 2 S d 2 S 1 10 PI C y Path difference Ax d sin 0 is applicable only when D d Path difference Ax yd D is applicable only when D y Almost equally spaced fringes near C only when D y Total number of maxima on the screen is 6 when d 3

Two coherent light sources radiate in phase The distance between sources is d where d 4 is the wavelength of incident light Figure The angles are measured from the line connecting the 2 sources The distance from the source to the point of observation is significantly larger than the wavelength Ny At 0 60 we observe a maxima At 0 30 we observe a minima At 0 60 we observe a minima At 0 30 we observe a maxima

In a single slit diffraction the first minimum is at angle 30 when light of wavelength 600 nm is used The angular position of first secondary maximum will be 1 sin 0 3 0 sin 2 3 1 2 2 0 sin 1 3 4 4 0 sin 1

1 5 is location of bright fringe l e there are 8 bright fringes and 7 minimal pls confirm the answer A bright fringe in Young s double slit experiment is 1 5 cm from the centre of the pattern The slit separation is 0 4 mm The light has a wavelength of 750 nm and falls on a screen 1 m away How many dark fringes are between the centre and the bright fringe at 1 5 cm Correct answer 8 User answer 7 Solution Answer 8 1 5 x 10 D n 750 10 1 0 4 x 10 9

White light is incident normally on a glass plate placed in air If the thickness of glass plate is 5000 A and its refractive index is 3 2 then among the following wavelength that is strongly reflected by the plates will be Visible light range is 4000 A to 7000 A 4700 A 6000 A 5500 A

There are two plane mirrors They are mutually inclined S is a source emitting light of wavelength The reflected beams interfere and fringe pattern is obtained on the screen If 0 is very small the fringe width will be 1 3 0 22 30 S F rti Je nulmelos a 4a 3 20 4 None of these