CBSE Class 12 Physics Wave Optics Worksheet Set A

CBSE Class 12 Physics Wave Optics Worksheet Set A

Question. A single slit diffraction pattern is obtained using a beam of red light. If the red light is replaced by the blue light, then the diffraction pattern
(a) remains unchanged
(b) becomes narrower
(c) becomes broader
(d) will disappear

Answer: B

Question. The idea of the quantum nature of light has emerged in an attempt to explain
(a) interference
(b) diffraction
(b) polarization
(d) radiation spectrum of a black body

Answer: D

Question. The deflection of light in a gravitational field was predicted first by
(a) Einstein
(b) Newton
(c) Max Planck
(d) Maxwell

Answer: B

Question. If a wave can be polarized, it must be
(a) a transverse wave
(b) a longitudinal wave
(c) a sound wave
(d) a stationary wave

Answer: A

Question. To demonstrate the phenomenon of interference, we require two sources which emit radiation of
(a) nearly the same frequency
(b) the same frequency
(c) different wavelengths
(d) the same frequency and having a definite phase relationship

Answer: D

Question. Angular width (B) of central maxima of a diffraction pattern of a single slit does not depend upon
(a) distance between slit and source
(b) wavelength of the light used
(c) width of slit
(d) frequency of light used

Answer: A

Question. The phenomenon by which stars recedes from each other is explained by
(a) black hole theory
(b) neutron star theory
(c) white dwarf
(d) red shift

Answer: D

Question. Interference was observed in an interference chamber when air was present. Now, the chamber is evacuated and if the same light is used, a careful observation will show
(a) no interference
(b) interference with bright bands
(c) interference with dark bands
(d) interference in which breadth of the fringe will be slightly increased

Answer: D

Question. Which of the following does not support the wave nature of light?
(a) Interference
(b) Diffraction
(c) Polarisation
(d) Photoelectric effect.

Answer: D

Question. The colours seen in the reflected white light from a thin oil film are due to
(a) diffraction
(b) interference
(c) polarisation
(d) dispersion

Answer: B

Question. The contrast in the fringes in an interference pattern depends on
(a) fringe width
(b) wavelength
(c) intensity ratio of the sources
(d) distance between the slits

Answer: C

Question. Which of the following phenomena is not common to sound and light waves ?
(a) Interference
(b) Diffraction
(c) Coherence
(d) Polarisation

Answer: D

Question. The phenomenon of interference is shown by
(a) longitudinal mechanical waves only
(b) transverse mechanical waves only
(c) non-mechanical transverse waves only
(d) All of the above

Answer: D

Question. Polarisation of light establishes
(a) corpuscular theory of light
(b) quantum nature of light
(c) transverse nature of light
(d) all of the three

Answer: C

Question. If the intensities of the two interfering beams in Young’s double-slit experiment are I₁ and I₂, then the contrast between the maximum and minimum intensities is good when
(a) | I₁ and I₂ | is large
(b) | I₁ and I₂ | is small
(c) either I₁ or I₂ is zero
(d) I₁ = I₂

Answer: D

Question. In Young's double slit experiment, if the slit widths are in the ratio 1 : 2, the ratio of the intensities at minima and maxima will be
(a) 1 : 2
(b) 1 : 3
(c) 1 : 4
(d) 1 : 9

Answer: D

Question. Which of the following cannot be polarised ?
(a) Radio waves
(b) β rays
(c) Infrared rays
(d) γ rays

Answer: B

Question. A nicol prism is based on the action of
(a) refraction
(b) double refraction
(c) dichroism
(d) both (b) and (c)

Answer: D

Question. Huygens concept of wavelets is useful in
(a) explaining polarisation
(b) determining focal length of the lenses
(c) determining chromatic aberration
(d) geometrical reconstruction of a wavefront

Answer: D

Question. Which one of the following phenomena is not explained by Huygens construction of wavefront?
(a) Refraction
(b) Reflection
(c) Diffraction
(d) Origin of spectra

Answer: D

Question. When a compact disc is illuminated by small source of white light, coloured bands are observed. This is due to
(a) dispersion
(b) diffraction
(c) interference
(d) reflection

Answer: B

Question. Interference is possible in
(a) light waves only
(b) sound waves only
(c) both light and sound waves
(d) neither light nor sound waves

Answer: C

Question. When light passing through rotating nicol is observed, no change in intensity is seen. What inference can be drawn ?
(a) The incident light is unpolarized.
(b) The incident light is circularly polarized.
(c) The incident light is unpolarized or circularly polarized.
(d) The incident light is unpolarized or circularly polarized or combination of both.

Answer: C

Question. In refraction, light waves are bent on passing from one medium to the second medium, because, in the second medium
(a) the frequency is different
(b) the coefficient of elasticity is different
(c) the speed is different
(d) the amplitude is smaller

Answer: C

Question. The transverse nature of light is shown by
(a) interference of light
(b) refraction of light
(c) polarization of light
(d) dispersion of light

Answer: C

Question. The max. intensity produced by two coherent sources of intensity I₁ and I₂ will be
(a) I₁ I₂
(b) I₁² I₂²
(c) I₁ + I₂ + 2√I₁ I₂
(d) zero

Answer: C

Question. Two points separated by a distance of 0.1 mm can just be inspected in a microscope, when light of wavelength 600Å is used. If the light of wavelength 4800 Å is used, the limit of resolution will become
(a) 0.80 mm
(b) 0.12 mm
(c) 0.10 mm
(d) 0.08 mm

Answer: D

Question. Two beams of light of intensity I₁ and I₂ interfere to give an interference pattern. If the ratio of maximum intensity to that of minimum intensity is 25/9, then I1/I2 is
(a) 5/3
(b) 4
(c) 81/625
(d) 16

Answer: D

Question. A parallel beam of light of wavelength l is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of the incident beam. At the second minimum of the diffraction pattern, the phase difference between the rays coming from the two edges of slit is 
(a) πλ
(b) 2π
(c) 3π
(d) 4π

Answer: D

Question. Two slits in Young’s experiment have widths in the ratio 1 :
25. The ratio of intensity at the maxima and minima in the interference pattern, Imax/Imin is:
(a) 121/49
(b) 49/121
(c) 4/9
(d) 9/4

Answer: D

Question. A slit of width a is illuminated by red light of wavelength 6500 Å. If the first minimum falls at θ = 30°, the value of a is
(a) 6.5 × 10^–4 mm
(b) 1.3 micron
(c) 3250 Å
(d) 2.6 × 10^–4 cm

Answer: B

Question. A single slit Fraunhoffer diffraction pattern is formed with white light. For what wavelength of light the third secondary maximum in the diffraction pattern coincides with the second secondary maximum in the pattern for red light of wavelength 6500 Å?
(a) 4400 Å
(b) 4100 Å
(c) 4642.8 Å
(d) 9100 Å

Answer: C

Question. Light of wavelength 6328 Å is incident normally on a slit having a width of 0.2 mm. The angular width of the central maximum measured from minimum to minimum of diffraction pattern on a screen 9.0 metres away will be about
(a) 0.36 degree
(b) 0.18 degree
(c) 0.72 degree
(d) 0.09 degree

Answer: A

Question. In Young’s double slit experiment, we get 10 fringes in the field of view of monochromatic light of wavelength 4000Å. If we use monochromatic light of wavelength 5000Å, then the number of fringes obtained in the same field of view is
(a) 8
(b) 10
(c) 40
(d) 50

Answer: A

Question. A plane wave of wavelength 6250 Å is incident normally on a slit of width 2 × 10^–2 cm. The width of the principal maximum on a screen distant 50 cm will be
(a) 312.5 × 10^–3 cm
(b) 312.5 × 10^–3 m
(c) 312.5 × 10^–3 m
(d) 312 m

Answer: A

Question. A ray of light strikes a glass plate at an angle of 60º. If the reflected and refracted rays are perpendicular to each other, the index of refraction of glass is
(a) 1/2
(b) √3/2
(c) 3/2
(d) 1.732

Answer: D

Question. The wavelength of Ha line in hydrogen spectrum was found to be 6563 Å in the laboratory. If the wavelength of same line in the spectrum of a milky way is observed to be 6568Å, then recession velocity of milky way will be
(a) 105 m/s
(b) 1.05 × 10⁶ m/s
(c) 10.5 × 10⁶ m/s
(d) 0.105 × 10⁶ m/s

Answer: B

Question. A star is receding away from earth with a velocity of 105 m/s. If the wavelength of its spectral line is 5700 Å, then Doppler shift will be
(a) 200 Å
(b) 1.9 Å
(c) 20 Å
(d) 0.2 Å

Answer: B

Question. A lens having focal length f and aperture of diameter d forms an image of intensity I. Aperture of diameter d/2 in central region of lens is covered by a black paper. Focal length of lens and intensity of image now will be respectively
(a) f and I/4
(b) 3f/4 and I/2
(c) f and 3I/4
(d) f/2 and I/2 

Answer: C

Question. The path difference between two wavefronts emitted by coherent sources of wavelength 5460Å is 2.1 micron. The phase difference between the wavefronts at that point is
(a) 7.692
(b) 7.692 π
(c) 7.692/π
(d) 7.692/3π

Answer: B

Question. The heavenly body is receding from earth, such that the fractional change in l is 1, then its velocity is
(a) c
(b) 3c/5
(c) c/5
(d) 2c/5

Answer: A

Question. In Young’s double slit expt. the distance between two sources is 0.1 mm. The distance of the screen from the source is 20 cm. Wavelength of light used is 5460 Å. The angular position of the first dark fringe is
(a) 0.08º
(b) 0.16º
(c) 0.20º
(d) 0.32º

Answer: B

Question. A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. If the speed of the electrons is increased, which of the following statements is correct ?
(a) The angular width of the central maximum of the diffraction pattern will increase.
(b) The angular width of the central maximum will decrease.
(c) The angular width of the central maximum will be unaffected.
(d) Diffraction pattern is not observed on the screen in case of electrons.

Answer: B

Question. Fluorescent tubes give more light than a filament bulb of same power because
(a) the tube contains gas at low temperature
(b) ultraviolet light is converted into visible light by fluorescence
(c) light is diffused through the walls of the tube
(d) it produces more heat than bulb

Answer: B

Question. Light from two coherent sources of the same amplitude A and wavelength l illuminates the screen. The intensity of the central maximum is I₀. If the sources were incoherent, the intensity at the same point will be
(a) 4I₀
(b) 1I₀
(c) I₀
(d) I₀/2

Answer: D

Question. In Young's double slit experiment with sodium vapour lamp of wavelength 589 nm and the slits 0.589 mm apart, the half angular width of the central maximum is
(a) sin^–1 (0.01)
(b) sin^–1 (0.0001)
(c) sin^–1 (0.001)
(d) sin^–1 (0.1)

Answer: C

Question. In Young’s double slit experiment the distance between the slits and the screen is doubled. The separation between the slits is reduced to half. As a result the fringe width
(a) is doubled 
(b) is halved
(c) becomes four times
(d) remains unchanged

Answer: C

Question. With a monochromatic light, the fringe-width obtained in a Young’s double slit experiment is 0.133 cm. The whole setup is immersed in water of refractive index 1.33, then the new fringe-width is
(a) 0.133 cm
(b) 0.1 cm
(c) 1.33 × 1.33 cm
(d) 1.33/2 cm

Answer: B

Question. The Fraunhoffer ‘diffraction’ pattern of a single slit is formed in the focal plane of a lens of focal length 1 m. The width of slit is 0.3 mm. If third minimum is formed at a distance of 5 mm from central maximum, then wavelength of light will be
(a) 5000 Å
(b) 2500 Å
(c) 7500 Å
(d) 8500 Å

Answer: A

Question. In Young’s expt., the distance between two slits is d/3 and the distance between the screen and the slits is 3 D. The number of fringes in 1/3 m on the screen, formed by monochromatic light of wavelength 3λ, will be
(a) 9/9Dλ
(b) d/27Dλ
(c) d/81 Dλ
(d) d/Dλ

Answer: C

Question. Two sources of light of wavelengths 2500 Å and 3500 Å are used in Young’s double slit expt. simultaneously. Which orders of fringes of two wavelength patterns coincide?
(a) 3rd order of 1st source and 5th of the 2nd
(b) 7th order of 1st and 5th order of 2nd
(c) 5th order of 1st and 3rd order of 2nd
(d) 5th order of 1st and 7th order of 2nd

Answer: B

Question. In a Young’s double-slit experiment, the source is white light. One of the holes is covered by a red filter and another by a blue filter. In this case,
(a) there shall be alternate interference patterns of red and blue
(b) there shall be an interference pattern for red distinct from that for blue
(c) there shall be no interference fringes
(d) there shall be an interference pattern for red mixing with one for blue

Answer: C

Question. In the phenomena of diffraction of light, when blue light is used in the experiment in spite of red light, then
(a) fringes will become narrower
(b) fringes will become broader
(c) no change in fringe width
(d) None of these

Answer: A

Question. In Young’s double slit experiment, the slits are 2 mm apart and are illuminated by photons of two wavelengths λ₁ = 12000Å and λ₂ = 10000Å. At what minimum distance from the common central bright fringe on the screen 2 m from the slit will a bright fringe from one interference pattern coincide with a bright fringe from the other ? 
(a) 6 mm
(b) 4 mm
(c) 3 mm
(d) 8 mm

Answer: A

Question. A slit of width a is illuminated by white light. The first minimum for red light (λ = 6500 Å) will fall at q = 30º when a will be
(a) 3250 Å
(b) 6.5 × 10^–4 cm
(c) 1.3 micron
(d) 2.6 × 10^–4 cm

Answer: C

Question. In Geiger-Marsden experiment, detection of scattered a-particles at a particular angle is done by
(a) counting flashes produced by a-particles on a ZnS coated screen
(b) counting spots produced on a photographic film
(c) using a galvanometer detector
(d) using a Geiger-counter

Answer : A

Question. Atoms consists of a positively charged nucleus is a consequence from the following observation of Geiger-Marsden experiment that
(a) most of a-particles do not pass straight through the gold foil
(b) very few a-particles scattered through an angle more than 90°
(c) very large number of a-particles are deflected by large angles
(d) None of the above

Answer : B

Question. If the orbital radius of the electron in a hydrogen atom is 4.7×10^-11 m. Compute the kinetic energy of the electron
in hydrogen atom.
(a) 15.3 eV
(b) - 15.3 eV
(c) 13.6 eV
(d) -13.6 eV

Answer : A

Question. The orbital radius of an electron in H-atom is increased by factor of 2, then the total energy of the electron will be
(a) decreased by 4
(b) increased by 2
(c) decreased by 2
(d) remain same

Answer : C

Question. An emission line spectrum is observed when
(a) a gas is excited by heating or by passing a electric discharge through it
(b) a gas is excited by applying pressure
(c) a gas under low pressure condition is excited by heating or by passing a electric discharge through it
(d) a gas under high pressure condition is excited by heating or by passing a electric discharge through it

Answer : C

Question. An electron of a hydrogen like atom is in excited state. If total energy of the electron is - 4.6 eV, then de-Broglie
wavelength of the electron is
(a) 6.27 nm
(b) 2.48 mm
(c) 0.57 nm
(d) 8 nm

Answer : C

Question. When white light is passed through an unexcited gas, then transmitted light consists of
(a) few bright lines in dark background
(b) few dark lines in bright background
(c) alternate dark and bright lines
(d) alternate dark and bright bands

Answer : B

Question. The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is
(a) 2
(b) 1
(c) 4
(d) 0.5

Answer : C

Question. Rutherford’s atomic model could account for
I. concept of stationary orbits.
II. the positively charged central core of an atom.
III. origin of spectra.
IV. stability of atoms.
Choose the correct option from the codes given below.
(a) Only I
(b) Only II
(c) I, III and IV
(d) I, II, III and IV

Answer : B

Question. It is found experimentally that 13.6 eV energy is required to separate a hydrogen atom into a proton and an electron.
Then, the velocity of the electron in a hydrogen atom is
(a) 10¹⁵ m/s
(b) 2.2×10⁶ m/s
(c) 4.2×10⁸ m/s
(d) 3×10⁸ m/s

Answer : B

Question. The ratio of speed of an electron in ground state in Bohr’s first orbit of hydrogen atom to the velocity of light in air is
(a) e²/2πhc 
(b) 2eπ/hc
(c) e³/2πhck
(d) 2πe²k/hc

Answer : D

Question. The speed of an electron in ground state energy level is 2.6×10⁶ms^-1, then its speed in third excited state will be
(a) 5.6×10⁶ms^-1
(b) 6.5×10⁵ ms^-1
(c) 5.5×10⁵ ms^-1
(d) 4.3×10⁶ ms^-1

Answer : B

Question. The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is
(a) 2 : - 1
(b) 1 : - 1
(c) 1 : 1
(d) 1 : - 2

Answer : B

Question. The total energy of an electron in an atom in an orbit is -3.4 eV. Its kinetic and potential energies are, respectively
(a) -3.4 eV, -6.8  eV
(b) 3.4 eV, -6.8 eV
(c) 3.4 eV, 3.4 eV
(d) - 3.4 eV, -3.4 eV

Answer : B

Question. If radius of first Bohr orbit is r,then the radius of second Bohr’s orbit will be
(a) 2r
(b) 8 r
(c) 4r
(d) 2 2r

Answer : C

Question. A 12.75 eV electron beam is used to bombard gaseous hydrogen at room temperature, then wavelengths emitted
are in
(a) either Paschen, Lyman or Balmer series
(b) either Brackett, Pfund or Lyman series
(c) either Paschen, Brackett or Balmer series
(d) either Lyman, Balmer or Brackett series

Answer : A

Question. The Bohr model for the spectra of a H-atom
(a) will not be applicable to hydrogen in the molecular form
(b) is applicable for multi-electron atom
(c) explain continuous as well as discrete spectral lines
(d) Both (a) and (b)

Answer : A

              Very Short Answer

Q1)       What is the speed of the wave?

Q2)       What is wavefront?

Q3)       Who discovered the true geometry of the Saturn’s rings?

Q4)       Who forward the wave theory of light?

Q5)       Who made the practical applications of the Hertzian waves?

             

              Short Answer

Q6)       What do you understand by the interference of light waves?

Q7)       What do you meant by Young’s experiment in wave’s optics?

Q8)       How does the light travel in a straight line?

Q9)       What do you understand by the coherent and incoherent addition of waves?

Q10)     What do you mean by the Huygens principle?

             

              Long Answer

Q11)     State the difference between the longitudinal waves and traverse waves?

Q12)     Explain about diffraction?

Q13)     Write short note on doppler effect?

Q14)     State the difference between diffraction and interference?

Q15)     Write short note on polarisation?