UNIT5 - EM WAVES & WAVE OPTICS- Tamil Nadu State Board Exam Questions - XII Plus Two

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Dear Students!
Following is the collection of all TN State Board Exam Questions (for Plus Two Physics) that appeared from March 2006 to September 2014. Answers for the MCQs and Problems will be uploaded soon. Pl note that the circuit diagrams are missing in this file; the same can be viewed in the pdf file uploaded in the same name as this file.

UNIT – V BOARD EXAM QUESTIONS

PART – I MAR 06 to SEP 14

The existence of electromagnetic waves was confirmed experimentally by M06
a] Hertz b] Maxwell c] Huygens d] Planck
When a drop of water is introduced between the glass plate and plano convex lens in Newton’s rings system, the ring system M06, J07, M08, J10, J11, J12, M14
a] contracts b] expands
c] remains the same d] first expands then contracts.
When a ray of light is incident on a glass surface at the polarising angle 57.50 , the angle between the incident ray and the reflected ray is M06, J06
a] 57.50 b] 32.50 c] 1150 d] 900
Unpolarised light passes through a tourmaline crystal. The emergent light is analysed by an analyser. When the analyser is rotated through 900, the intensity of light M06
a] remains uniformly bright b] remains uniformly dark
c] varies bet. maximum and minimum d] varies bet. maximum and zero
In an electromagnetic wave, the phase difference between electric field E and magnetic field B is
J06, J08, S08, M09, J10, M11, J13, J14
a] π / 4 b] π / 2 c] π d] zero
Velocity of electromagnetic waves through vacuum is J06
a] √(µ_0 ε_0 ) b] 1/√(µ_0 ε_0 ) c] √(µ_0/ε_0 ) d] √(ε_0/µ_0 )
In a plane transmission grating, the unit of grating element is J06, J13
a] no unit b] m c] m– 1 d] degree
Which one of the following is not an electromagnetic wave? S 06
a] X-rays b] γ – rays c] U V rays d] β – rays
If ‘c’ is the velocity of light in vacuum, the velocity of light in a medium of refractive index μ is S 06
a] μ c b] c / μ c] μ / c d] 1 / μ c
A ray of light passes from a denser medium into a rarer medium. For an angle of incidence of 450 , the refracted ray grazes the surface of separation of the two media. The refractive index of the denser medium is S 06
a] 3 / 2 b] 1 / √2 c] √2 d] 2
Of the following, which one is a uniaxial crystal? S 06
a] Mica b] Aragonite c] Topaz d] Quartz
The radiations used in physiotherapy are M 07
a] ultraviolet b] infrared c] radio waves d] micro waves
In Newton’s rings experiment, light of wavelength 5890 Å is used. The order of the dark
ring produced when the thickness of the air film is 0.589 μ m is M 07
a] 2 b] 3 c] 4 d] 5
Atomic spectrum should be _________ spectrum. M07, J12, J14
a] pure line b] emission band c] absorption line d] absorption band
Of the following, the optically active material is M 07
a] sodium chloride b] calcium chloride c] sodium d] chlorine
A diffraction pattern is obtained using a beam of red light. What happens if the red light is replaced by blue light? J 07, J 08, M 11, S 11
a] Bands disappear b] No change
c] Diffraction pattern becomes narrower and crowded together
d] Diffraction pattern becomes broader and farther apart.
Electric filament lamp gives rise to _______ spectrum. J 07
a] line b] continuous c] band d] line absorption
In Young’s double-slit experiment, the separation bet. the slits is halved and the distance between the slits and the screen is doubled. Then the fringe width is [ J 07 ]
a] unchanged b] halved c] doubled d] quadrupled
The phenomenon of light used in Newton’s rings is [ S 07 ]
a] diffraction b] interference c] refraction d] polarisation
An example for uniaxial crystal is S07, S11, S14
a] tourmaline (calcite) b] mica c] topaz d] selenite.
In Raman effect, spectral line with lower frequency than incident frequency is S 07
a] Fraunhofer line b] Rayleigh line c] Stokes’ line d] anti-Stokes’ line.
The optical rotation does not depend on S 07
a] concentration of the solution b] frequency of the light used
c] temperature of the solution d] intensity of the light used.
Which of the following gives rise to continuous emission spectrum? M 08
a] Electric filament lamp b] Sodium vapour lamp
c] Gases in the discharge tube d] Calcium salt in bunsen flame
A light of wavelength 6000 Å is incident normally on a grating 0.005 m wide with 2500 lines. Then the maximum order is M08, M13, S13
a] 3 b] 2 c] 1 d] 4
The transverse nature of light waves is demonstrated by the phenomenon of M 08
a] interference b] diffraction c] polarisation d] reflection
If the velocity of light in a medium is 2.25 x 108 m s – 1 , then the refractive index of the medium will be J 08
a] 1.5 b] 0.5 c] 1.33 d] 1.73
The polarising angle for water is 530 4'. If the light is incident at this angle on the surface of water, the angle of refraction in water is J08, M13
a] 530 4' b] 260 30' c] 300 4 ' d] 360 56'
The refractive index of a medium with a polarising angle of 600 is S 08, M10, J13
a] 1.732 b] 1.414 c] 1.5 d] 1.468
In Raman effect, if the scattered photon gains energy, it gives rise to _______ lines. S08, S13
a] Stokes’ b] anti-Stokes’ c] Stokes’ and anti-Stokes’ d] Rayleigh
In the case of Fraunhofer diffraction, the wave front undergoing diffraction is S 08
a] spherical b] cylindrical c] elliptical d] plane
A ray of light is incident on a glass surface such that the reflected ray is completely plane
polarised. The angle between the reflected and the refracted ray is M 09
a] 57.50 b] 32.50 c] 900 d] 1150
Soap bubbles exhibit brilliant colours in sunlight due to ______ of light. M 09
a] scattering b] diffraction c] polarization d] interference
The radii of Newton’s dark rings are in the ratio M 09
a] 1:2:3… b] √1 : √2 : √3 … c] √1 : √3 : √5 … d] 1 : 4 :9 …
In an electromagnetic wave J09, S13, M14, S14
a] power is equally transferred along the electric and magnetic fields
b] power is transmitted in a direction perpendicular to both the fields
c] power is transmitted along electric field
d] power is transmitted along magnetic field.
In the grating formula sin θ = Nmλ , the unit of N is J 09, J 10
a] metre b] metre –1 c] no unit d] (metre) 2
If the wavelength of the light is reduced to one fourth, then the amount of scattering is
J 09 , M 10
a] increased by 16 times b] decreased by 16 times
c] increased by 256 times d] decreased by 256 times
The ratio of radii of the 4th and the 9th dark rings in Newton’s rings experiment is J 09
a] 4 : 9 b] 2 : 3 c] 16 : 81 d] √2 : √3
Electromagnetic waves are S09, S10, J11, M13
a] transverse b] longitudinal
c] may be longitudinal or transverse d] neither longitudinal nor transverse.
In Newton’s ring experiment, the radii of m th and (m+4) th dark rings are respectively
√5 mm and √7 mm . What is the value of m ? S 09
a] 2 b] 4 c] 8 d] 10
Atomic spectrum should be ______ spectrum. S 09
a] pure line b] emission band c] absorption line d] absorption band
Which of the following is not an optically active material? S 09
a] Quartz b] Sugar crystals c] Turpentine d] Calcium chloride
In Raman effect, the incident photon makes collision with an excited molecule of the substance. The scattered photon gives rise to ____. M 10
a] Stokes’ line b] anti-Stokes’ line c] Rayleigh line d] Zeeman line
The refractive index of glass is 1.5 . The velocity of light in glass is M 10
a] 2 x 10 8 ms – 1 b] 4.5 x 10 8 ms – 1 c] 3 x 10 8 ms – 1 d] 1.33 x 10 8 ms – 1
The transverse nature of light waves is demonstrated by the phenomenon of J 10
a] interference b] diffraction c] polarization d] reflection
The dark lines found in the solar spectrum are called ______ lines. S 10
a] Raman b] Fraunhofer c] Stokes’ d] anti-Stokes’
In Young’s experiment, the third bright band for wavelength of light 6000 Å coincides with the fourth bright band for another source in the same arrangement. The wave length of the another source is S 10
a] 4500 Å b] 6000 Å c] 5000 Å d] 4000 Å
A ray of light travelling in a rarer medium and reflected at the surface of a denser medium automatically undergoes a S 10
a] phase change of π/2 b] phase change of 2π
c] path diff. of λ d] path diff. of λ/2.
Waves from two coherent sources interfere with each other. At a point where the trough of one wave superposes with the trough of the other wave, intensity of light is M 11
a] maximum b] minimum c] zero d] no change.
Refractive index of glass is 1.5 .Time taken for light to pass through a glass plate of thickness 10 cm is M11, S14
a] 2 x 10 – 8 s b] 2 x 10 – 10 s c] 5 x 10 – 8 s d] 5 x 10 – 10 s.
The nature of the wavefront corresponding to extraordinary ray inside a calcite crystal is J 11
a] plane b] spherical c] elliptical d] cylindrical.
A ray of light is incident on a plane glass surface at an angle of 57 0 30 ‘ . The angle between the reflected ray and the refracted ray is J 11
a] 57 0 30 ‘ b] 90 0 c] 115 0 d] 57 0 30 ‘.
In a pile of plates arrangement, the angle between the incident and the reflected plane polarized light is S 11
a] 32.5 0 b] 57.5 0 c] 90 0 d] 115 0 .
Refractive index of a material for a polarising angle of 55 0 is J12
a] 1.4281 b] 1.7321 c] 1.4141 d] 1.5051.
In a Nicol prism, the ordinary ray is prevented from coming out of Canada balsam by the phenomenon of J12
a] reflection b] polarisation c] diffraction d] total internal reflection.
In Young’s double slit experiment, bandwidth β contains M13
a] a bright band only b] a dark band only
c] either a bright band or a dark band d] both a bright band and a dark band.
The path difference between two monochromatic light waves of wavelength 4000 Å is 2 × 10−7 m. The phase difference between them is J13
a] π b] 2π c] 3π/2 d] π/2 .
According to Foucault and Michelson experiment the velocity of light in a rarer medium is: S13
a] greater than in a denser medium b] lesser than in a denser medium
c] equal to that in a denser medium d] either greater or lesser than in a denser medium.
The characteristic spectrum of an atom is observed as: M14
a] pure line spectrum b] emission band spectrum
c] absorption line spectrum d] absorption band spectrum.
Which of the following is a biaxial crystal? M14
a] Calcite b] quartz c] tourmaline d] topaz.
In Newton's ring experiment the radii of the mth and (m+4)th dark rings are respectively
√5 mm and √7 mm. What is the value of m ? J14
a] 2 b] 4 c] 8 d] 10.
A ray of light is incident on a glass plate at polarizing angle. The angle between the incident and the reflected ray is J14
a] 57.50 b] 900 c] 1150 d] 32.50.
The scattering of sunlight by gas molecules in the earth’s atmosphere is: S14
a] Raman’s effect b] α-scattering c] Tyndall scattering d] Rayleigh scattering.



PART – II THREE – MARK QUESTIONS
What are emission and absorption spectra? M06
A 300 mm long tube containing 60 cc of sugar solution produces a rotation of 9 0 when placed in a polarimeter. If the specific rotation is 60 0, calculate the quantity of sugar contained in the solution.
M06, M09
Why does the sky appear blue in colour? J06
In Young’s experiment, the width of the fringes obtained with light of wavelength 6000 Å is 2 mm. Calculate the fringe width if the entire apparatus is immersed in a liquid of refractive index 1.33.
J06, M11, S14
What is band emission spectrum? Give an example. S06
A light of wavelength 6000 Å falls normally on a thin air film, 6 dark fringes are seen between two points. Calculate the thickness of the air film. S06, J08, J11
What is Tyndall scattering? M07, J09, J10, S10, J13
In Newton’s rings experiment the diameter of certain order of dark ring is measured to be double that of second ring. What is the order of the ring? M07, J07, S11
Define optic axis of a crystal. J07, J10
Distinguish between interference and diffraction fringes. S07
A light of wavelength 5890 Å falls normally on a thin air film, 6 dark fringes are seen between two points. Calculate the thickness of the air film. S07
Two slits 0.3 mm apart are illuminated by light of wavelength 4500 Å. The screen is placed at 1 m distance from the slits. Find the separation between the second bright fringe on both sides of the central maximum. M08
Define specific rotation. M08, M10
On what factors does the amount of optical rotation depend? J08, J11
Write any three uses of infrared radiations. S08
Write the conditions for total internal reflection to take place. S08, M14
Why is the centre of the Newton’s rings dark? M09, J13
A light of wavelength 6000 Å falls normally on a thin air film, 6 dark fringes are seen between two points. Calculate the thickness of the air film. J09
The refractive index of a medium is √3 . Calculate the angle of refraction if the unpolarised light is incident on it at the polarizing angle of the medium. S09
State Huygens’ principle. S09, S11
Define specific rotation. M10, S13, J14
Distinguish between Fresnel and Fraunhofer diffractions. M10, J12
A plano–convex lens of radius 3 m is placed on an optically flat glass plate and is illuminated by monochromatic light. The radius of the 8th dark ring is 3.6 mm. Calculate the wavelength of light
used. S10, J12
State Brewster’s law. M11
What are Fraunhofer lines? M13
An LC resonant circuit contains a capacitor 400 pF and an inductor 100 µH. It is set into oscillations coupled to an antenna. Calculate the wavelength of the radiated electromagnetic wave. M13
Why the sky appears blue in colour? S13, J14
Give the uses of ultraviolet radiations. M14
List the conditions for sustained interference. S14

PART – III FIVE – MARK QUESTIONS
Write a note on pile of plates. M06, J09
State and prove Brewster’s law. J06 , S06, J07, J08, M09, J10, S12, M13
Write a note on Nicol prism. M07, S09, S11
[a] A soap film of refractive index 1.34, is illuminated by white light incident at an angle 300. The reflected light is examined by spectroscope in which dark band corresponding to the wavelength 5893Å is found. Calculate the smallest thickness of the film. [OR]
[b] In Young’s experiment a light of frequency 6 × 1014 Hz is used. Distance between the centres of adjacent fringes is 0.75 mm. Calculate the distance between the slits, if the screen is 1.5 m away. S07(Compulsory)
A parallel beam of monochromatic light is allowed to incident normally on a plane transmission grating having 5000 lines per cm. A second order spectral line is found to be diffracted at an angle
30 0. Find the wavelength of the light. M08, J12
Q. No. 4 [a] S08
a] A parallel beam of monochromatic light is allowed to incident normally on a plane transmission grating having 5000 lines per cm. A second order spectral line is found to be diffracted at an angle of 30 0. Find the wavelength of the light. [ OR ]
b] In a Newton’s rings experiment the diameter of the 20 th dark ring was found to be 5.82 mm and that of the 10 th ring is 3.36 mm. If the radius of the plano-convex lens is 1 m, calculate the wavelength of the light used. M10 (Compulsory), 7b] M14
Distinguish between interference and diffraction. S10
a] A monochromatic light of wavelength 589 nm is incident on a water surface having refractive index 1.33. Find the velocity, frequency and wavelength of light in water. OR
b] A plano–convex lens of radius 3 m is placed on an optically flat glass plate and is illuminated by monochromatic light. The radius of 8th dark ring is 3.6 mm. Calculate the wavelength of light used.
M11 (Compulsory)
Obtain the expression for the radius of the nth dark ring in Newton’s rings experiment.
J11, M12
a] A plane transmission grating has 5000 lines / cm. Calculate the angular separation in second order spectrum of red line 7070 Å and blue line 5000 Å. OR
b] A 300 mm long tube containing 60 cc of sugar solution produces a rotation of 90 when placed in a polarimeter. If the specific rotation is 60 0, calculate the quantity of sugar contained in the solution.
J13 (Compulsory)V
A soap film of refractive index 1.33 is illuminated by white light incident at an angle 300. The reflected light is examined by spectroscope in which dark band corresponding io the wavelength 6000 A is found. Calculate the smallest thickness of the film. S13
In Newton's Ring experiment the diameter of certain order of dark ring is measured to be double that of second ring. What js the order of the ring ? J14
In Young’s double slit experiment two coherent sources of intensity ratio of 64:1 produce interference fringes. Calculate the ratio of maximum and minimum intensities. S14

PART – IV TEN – MARK QUESTIONS
On the basis of the wave theory, explain total internal reflection. M06, S13
Q. No. 1 + Write the conditions for the total internal reflection to take place. J06
Derive an expression for the bandwidth of interference fringes in Young’s double-slit experiment.
S06, J07, M09, J10, S10, M11, S11, M14, J14
Explain Raman scattering of light with the help of energy-level diagram. M07, S07,J11, M13, S14
What is Raman effect? Explain Raman spectrum with diagram. M08
Discuss the theory of interference in thin transparent film due to reflected light and obtain the condition for the intensity to be maximum and minimum. J08, S09
State Huygens’ principle. On the basis of wave theory, prove the laws of reflection. S08
Explain emission and absorption spectra. J09, M10, M12, J12, S12
What is emission and absorption spectra? Explain the different types of emission and absorption spectra with examples. J13