CET –VIKASANA-2014 II PUC PHYSICS CHAPTER : 10...
Transcript of CET –VIKASANA-2014 II PUC PHYSICS CHAPTER : 10...
VVCET –VIKASANA-2014
II PUC
CET –VIKASANA-2014
II PUCII PUC
PHYSICS
II PUC
PHYSICSPHYSICS
CHAPTER : 10
PHYSICS
CHAPTER : 10 CHAPTER : 10
WAVE OPTICS
CHAPTER : 10
WAVE OPTICSWAVE OPTICSWAVE OPTICS
SYNOPSISSYNOPSISWavefront: Surface of constant phasep
At small distance:
P i S h i l fPoint source – Spherical wavefront
Linear source – Cylindrical wavefronty
At large distance:P i Li Pl fPoint source, Linear source – Plane wavefront
Behaviour of the wavefronts on reflection andBehaviour of the wavefronts on reflection and refraction:
When a plane wavefront incident on pa thin prism, emergent wavefront is plane.convex lens, the emergent wavefront is, gspherical convergent wavefront.concave lens, the emergent wavefront isspherical divergent wavefront.concave mirror, the reflected wavefront isspherical convergent wavefrontspherical convergent wavefront.convex mirror, the reflected wavefront isspherical divergent wavefrontspherical divergent wavefront.
DOPPLER EFFECTDOPPLER EFFECT• The apparent change in frequency of the light due to relative motion betweenlight due to relative motion between source and observer.
• Red shift: When the source moves away• Red shift: When the source moves away from the observer, there is decrease in frequency or increase in wavelength.frequency or increase in wavelength.
• Blue shift: When the source is moving towards the observer, there is antowards the observer, there is an increase in frequency or decrease in wavelength.g
INTERFERENCE OF LIGHTINTERFERENCE OF LIGHT Interference can occur only with coherent sources. But two independent sources cannot be coherent.
S1 : y1 = a cos(ωt) and S2 : y2= a cos(ωt + φ)y = y + y = [2a cos (φ/2)] cos (ωt + φ/2)y = y1 + y2 = [2a cos (φ/2)] cos (ωt + φ/2)Resultant amplitude: R = 2a cos (φ/2)
Resultant intensity: I = 4 I0 cos2 (φ/2)
POLARIZATION BY REFLECTION:POLARIZATION BY REFLECTION:Brewster’s law: n = tan iB
r + iB = 90°
The reflected andThe reflected and
the refracted rays are
perpendicular to each other.
At Brewster’s angle of incidence, the
reflected light is completely polarized.reflected light is completely polarized.
1) Whi h f th f ll i h1) Which of the following phenomenon cannot produce colours with white light?
1) Dispersion
2) Interference2) Interference
3) Diffraction
4) Polarization
2) F li ht di i f i t2) For light diverging from a point source
(1) The wavefront is spherical.( ) p
(2) The wavefront is plane.
(3) Th i i i i i(3) The intensity increases in proportion to the distance squared.
(4) The intensity at the wavefront does not depend on the distancenot depend on the distance.
3) Whi h f th f ll i h3) Which of the following graph represents the variation of fringe width(β)with the distance between the slits (d) is
ββ β βββ β β
d d d d
4) F i t f t b b d th4) For interference to be observed, the source of light should be
(a) coherent (b) narrow (c) closer
1) (a) is correct1) (a) is correct
2) (b) and (c) are correct
3) (a) and (b) is correct
4) (a) (b) and (c) is correct4) (a),(b) and (c) is correct
5) Th i f i t i t5) The image of a point source is not a point, but has a definite size this is due to phenomenon of
1) Interference1) Interference
2) Diffraction
3) Refraction
4) Dispersion4) Dispersion
6) Th I t f h i6) The Interference phenomenon is observed
1) only in transverse waves
2) only in longitudinal waves2) only in longitudinal waves
3) both types of waves
4) not observed in both type of waves
7) Whi h f th f ll i t b7) Which of the following cannot be polarized?
1) Radio waves
2) Ultrasonic waves2) Ultrasonic waves
3) Light waves
4) X – rays
8) It i diffi lt t b diff ti i8) It is difficult to observe diffraction in case of light waves, because
1) Speed of light is more
2) Light waves are transverse in nature2) Light waves are transverse in nature
3) Light waves can travel through vacuum
4) Wave length of light is small.
9) Whi h f h f ll i i9) Which of the following is correct relation between the wave front and the ray of light? The ray of light1) Is tangential to the wave front1) Is tangential to the wave front
2) Is normal to wave front
3) Can be inclined at any angle with the wave front.
4) Does not exist according to the Huygen’s principle
10) Whi h f th f ll i i WRONG10) Which of the following is WRONG about light according to the corpuscular theory? 1) Light travels in straight lines ) g g
2) The velocity of light is more in air than in waterwater
3) The velocity of light changes on refraction
)4) The velocity of light does not change on reflection
11) Wh li ht f l th 480 i11) When light of wavelength 480nm is used, 12 fringes are obtained on a certain region of the screen in Young's double slit experiment . When light of wavelength p g g640nm is used, the number of fringes obtained in the same region areobtained in the same region are
1) 8 2) 9
3) 11 4) 12
12) S1 and S2 are two coherent sources.
Th i i f b hThe intensity of both sources are same.
If the intensity at the point of maxima isIf the intensity at the point of maxima is
4 Wm– 2 the intensity of each source is4 Wm , the intensity of each source is
1) 1 Wm– 2 2) 2 Wm– 2
3) 3 Wm– 2 4) 4 Wm– 2
AAnswer:
At the point of maximaAt the point of maxima,
I = 4 I = 4 Wm– 2Imax = 4 Io = 4 Wm 2
I = 1 Wm– 2Io = 1 Wm 2
Answer: (1)Answer: (1)
13) In an interference experiment using13) In an interference experiment using waves of same amplitude, path difference b t th t i t thbetween the waves at a point on the screen is λ/4. The ratio of intensity at this point with that at the central bright fringe is g g1) 1 : 2 2) 2 : 1
3) 1 : 4 4) 4 : 1
14) To increase both the resolving power14) To increase both the resolving power and magnifying power of a telescope1) both the focal length and aperture of the objective has to be increased 2) the wavelength of light has to be decreased3) the focal length of the objective has to be increasedbe increased 4) the aperture of the objective has to be increasedincreased
15) L diff i i15) Largest diffraction is undergone in the case ofundergone in the case of
1) γ‐rays 2) Ultraviolet light
3) Red light
4) R di4) Radio waves
AAnswer:
θ ∝ λ
γ‐rays , X‐rays, Ultraviolet rays, Visible light,
Infra red rays, Microwaves, Radio waves.
Answer (4): Radio waves.
17) Th i t f diff f diff ti i th t17) The interference differs from diffraction in that,
1) It cannot be observed with white light .
2) Unlike diffraction the interference fringes
f i i t itare of varying intensity.
3) Interference minima are perfectly dark and ) p y
that of diffraction may not be dark.
)4) The diffraction fringes are of equal width but
the interference fringes are of unequal width.
18) If ll li h l bl li h18) If yellow light replaces blue light in Young’s double slit experiment. g p
The fringes will become
1) Wider 2) Narrower
3) Brighter 4) Fainter3) Brighter 4) Fainter
19) Diffraction pattern is observed using19) Diffraction pattern is observed using green light . When green light is replaced by red lightby red light1) No change is observed2) Bands become narrower and crowded3) Bands become broader and well3) Bands become broader and well
separated) d di4) Bands disappear.
20) A d bl lit t i i d i20) A double slit apparatus is immersed in a liquid of R.I. 1.5. It has slit separation of 1 mm and distance between the plane of slits and screen 1.5 m. The slits are lit by a yparallel beam of monochromatic light. Given the wave length in air is 4500 Å.Given the wave length in air is 4500 Å.
Then fringe width is equal to
1) 0.3 mm 2) 0.45 mm
3) 0 675 mm 4) 4 5 mm3) 0.675 mm 4) 4.5 mm
21) Two slits separated by a distance of21) Two slits separated by a distance of 1.2 mm are illuminated with light of
l h h i fwavelength 600 nm. The interference fringes observed on a screen placed 120 cm from the slits. The distance between third dark fringe and the sixth bright g gfringe is 1) 0 60 mm 2) 1 5 mm1) 0.60 mm 2) 1.5 mm 3) 2.1 mm 4) 4.5 mm
22) I Y ’ d bl li i22) In Young’s doubles slit experiment, the screen is moved towards the slits by 10 cm, so that the change is fringe with is 40 µmwith is 40 µm.
If the distance between two slits is 1.5mm, the wavelength of light used is
1) 500 2) 6001) 500nm 2) 600nm
3)700nm 4) 800nm3)700nm 4) 800nm
23) The wavelength of light whose third
secondary maximum coincides with thesecondary maximum coincides with the
second minimum of red light of wavelength
630 nm in a single slit diffraction is
1) 720 nm 2) 420 nm
3) 630 4) 3603) 630 nm 4) 360 nm
24) Th li ht f t i d d t24) The light waves from two independent monochromatic light sources are given by
y1 = 2 sin ωt and y2 = 3 cos ωt. Then the correct statement isThen the correct statement is 1) Both the waves are coherent
2) Both the waves are incoherent
3) Both the waves have different time periods ) p
4) Both the waves have same phase
) h i li h f25) A monochromatic light of wavelength 700 nm is incident on a 3.5 gmm wide aperture. What is the di hi h h f li hdistance up to which the ray of light can travel so that its spread is less than ca t a e so t at ts sp ead s ess t athe size of the aperture? 1) 0.5 m 2) 18.5 m
3) 17.5 m 4) 15.7 m3) 17.5 m 4) 15.7 m
26) In the case of diffraction pattern due
to a single slit linear width of centralto a single slit, linear width of central
maximum can be increased byy
1) decreasing the wavelength2) i i h li id h2) increasing the slit width.3) decreasing distance between slit and screen.4) decreasing the slit width.4) decreasing the slit width.
27) Match the following names of physicist27) Match the following names of physicist with their contribution:
a) NEWTON (i) WAVE THEORY OF LIGHTb) HUYGENS (ii) INTERFERENCE OF LIGHTb) HUYGENS (ii) INTERFERENCE OF LIGHTc) MAXWELL (iii) CORPUSCULAR MODEL OF LIGHT
d) ( )d) THOMAS YOUNG
(iv) ELECTROMAGNETIC THEORY OF LIGHT
1) a– iii, b– i, c– iv, d– ii. 2) a– iv, b– ii, c– i, d–iii. 3) a ii b iii c i d iv 4) a ii b iv c i d iii3) a– ii, b– iii, c– i, d– iv. 4) a– ii, b– iv, c– i, d– iii.
28) An optical instrument resolves two
i di f i i li h fpoints at a distance from it using light of
wavelengths 450nm and 600nm the ratiowavelengths 450nm and 600nm, the ratio
of their respective resolving powers is p g p
1) 4 : 3 2) 3 : 4
3) 16 : 9 4) 9 : 25
29) Li ht f l th 628 i i id t29) Light of wavelength 628 nm is incident on slit having a width of 0.2 mm. The angular width of the central maximum, measured from minimum to minimum of the diffraction pattern on a screen 2.0 m away will be aboutaway will be about
1) 0.036o 2) 0.18 o
3) 0.36 o 4) 0.628 o
31) U l i d li ht f i t it 32 W/ 231) Unpolarised light of intensity 32 W/m2
is incident on the combination of two polaroids. If the intensity of the light transmitted through the combination is g
8 W/m2, what is the angle between the transmission axes of Polaroid’s?transmission axes of Polaroid s?
1) 00 2) 300 3) 450 4) 600
Answer:Answer:
Unpolarised light polarised light transmitted light
32 W/m2 16 W/m2 (50%) 4 W/m2
Polaroid‐1 Polaroid‐2
I = I0 cos2θI I0 cos θ⇒ 8 = 16 cos2 θ⇒ cos2 θ =1/2⇒ cos θ =1/2
⇒ θ = 45o
Answer (3)Answer (3)
32 Which of the following relation is32. Which of the following relation is correct for a medium with polarising angle i corresponding angle ofangle ‐ iB , corresponding angle of refraction‐ r and critical angle ‐ iC ?
11) r = tan−1(sin iC) 2) r = 1/[tan−1(sin iC)] ) /[ ( C)]3) r = tan−1 (cos iC)4) r = tan−1 (1/sin i )4) r = tan 1 (1/sin iC)
33 Th h d li ht f j 1 233. 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 589.6nm is used, what g ,should be the maximum distance of the jeep from the observer if the twojeep from the observer if the two headlights are just separated?
1) 3 39 2)33 91) 3.39 m 2)33.9 m
3) 3.39 km 4) 33.9 km) )
34. A ray of light is incident on the
surface of a medium whosesurface of a medium, whose
refractive index is 1.732 at polarizing
angle. The angle of incidence and
angle of refraction are respectively
1) 25o 30o 2) 350 30o1) 25o , 30o 2) 350, 30o
3) 30o, 60o 4) 60o , 30o) , ) ,
35. Two points are separated by 0.1 mm can
just be inspected in a microscope, when thej p p ,
light of wa
velength 600nm is used.
If the light of a elength 480nm is sed theIf the light of wavelength 480nm is used, the
limit of resolution will be1) 0.1mm 2) 0.12mm3) 0.08mm 4) 0.8mm) )
36 Two similar polaroids are placed36. Two similar polaroids are placedsuch that they cross each other. Then
f h i d h hone of them is rotated through anangle 30o. Unpolarised light is made toincident on first polaroid. Whatpercentage of incident light will passp g g pthrough the system?1) 37 5% 2) 87 5%1) 37.5% 2) 87.5%3) 50% 4) 12.5%
ANSWER:ANSWER:Unpolarised light polarised light transmitted light
100% 50% (I0) I = ?Polaroid‐1 Polaroid‐2Polaroid 1 Polaroid 2
I = I0 cos2θcos2 θ = cos2 60o = cos2 θ =1/4cos2 θ = cos2 60o = cos2 θ =1/4
⇒ I = (50%)(1/4) = 12.5 %Answer (4)