Title WAVE OPTICS.docx.pdf ✅

10.WAVE OPTICS Single Correct Answer Type 1. The phenomenon of polarization of light indicates that a) Light is a longitudinal wave b) Light is a transverse wave c) Light is not a wave d) Light travels with the velocity of 3×10 8 ms −1 2. Diffraction and interference of light suggest a) Nature of light is electro-magnetic b) Wave nature c) Nature is quantum d) Nature of light is transverse 3. The 21 cm radio wave emitted by hydrogen in interstellar space is due to the interaction called the hyperfine interaction is atomic hydrogen. the energy of the emitted wave is nearly a) 10 −17 Joule b) 1 Joule c) 7×10 −8 Joule d) 10 −24 Joule 4. The fringe width in Young’s double slit experiment increases when a) Wavelength increases b) Distance between the slits increases c) Distance between the source and screen decreases d) The width of the slits increases 5. Biological importance of Ozone layer is a) It stops ultraviolet rays b) Ozone rays reduce green house effect c) Ozone layer reflects radio waves d) Ozone layer controls O radio in atmosphere 2 /H 2 6. A parallel beam of light of intensity I is incident on a glass plate, 25% of light is reflected by upper surface 0 and 50% of light is reflected from lower surface. The ratio of maximum to minimum intensity in interference region of reflected rays is a) 1 2 + 3 8 1 2 − 3 8 ( ) 2 b) 1 4 + 3 8 1 2 − 3 8 ( ) 2 c) 5 8 d) 8 5 7. A beam of ordinary unpolarised light passes through a tourmaline crystal C and then it passes through 1 another tourmaline crystal C , which is oriented such that its principal plane is parallel to that of . The 2 C 2 intensity if emergent light isI . Now is rotated by about the ray. The emergent ray will have an 0 C 2 60° intensity a) 2I 0 b) I 0 /2 c) I 0 /4 d) I 0 / 2 8. Which one of the following is INCORRECT statement in the transmission of electromagnetic waves Page| 1
a) Ground wave propagation is for high frequency transmission b) Sky wave propagation is facilitated by ionospheric c) Space wave is of high frequency and is suitable for line of sight communication d) Space wave is used for satellite communication 9. Find the thickness of a plate which will produce a change in optical path equal to half the wavelength λ of the light passing through it normally. The refractive index of the plate μ is a) λ 4(μ−1) b) 2λ 4(μ−1) c) λ (μ−1) d) λ 2(μ−1) 10. Critical angle for certain medium is (0. 6). The polarizing angle of that medium is a) [1. 5] b) [0. 8] c) [1. 6667] d) [0. 6667] 11. Electromagnetic waves can be deflected by a) Electric field only b) Magnetic field only c) Both (a) and (b) d) None of these 12. If c is the speed of electromagnetic waves in vacuum, its speed in a medium of dielectric constant K and relative permeability μ is r a) v = 1 μ r K b) v = c μ r K c) v = c μ r K d) v = K μ r C 13. In Young’s double slit experiment a minima is observed when path difference between the interfering beam is a) λ b) 1. 5λ c) 2λ d) 2. 25λ 14. When the angle of incidence on a material is 60°, the reflected light is completely polarized. The velocity of the refracted ray inside the material is (in ms ) −1 a) 3×10 8 b) 3 ( 2 ) × 10 8 c) 3 × 10 8 d) 0. 5 × 10 8 15. A parallel monochromatic beam of light is incident normally on a narrow slit. A diffraction pattern is formed on a screen placed perpendicular to the direction of incident beam. At the first maxima of the diffraction pattern the phase difference between the rays coming from the edges of the slit is a) 0 b) π 2 c) π d) 2π 16. Light waves can be polarized as they are a) Transverse b) Of high frequency c) Longitudinal d) Reflected 17. A diffraction pattern is obtained using a beam of red light. What happens if the red light is replaced by blue light a) No change b) Diffraction bands become narrower and crowded together c) Band become broader and farther apart d) Bands disappear altogether 18. A Young’s double slit set up for interference is shifted from air to within water, then the fringe width Page| 2
a) Becomes infinite b) Decreases c) Increases d) Remain unchanged 19. Ordinary light incident on a glass slab at the polarising angle, suffers a deviation of22°. The value of the angle of refraction in glass in this case is a) 56° b) 68° c) 34° d) 22° 20. The waves of wavelength 5900 Å emitted by any atom or molecule must have some finite total length which is known as coherence length. For sodium light, this length is 2. 4 cm. The number of oscillations in this length will be a) 4. 068×10 8 b) 4. 068×10 4 c) 4. 068×10 6 d) 4. 068×10 5 21. The width of a single slit if the first minimum is observed at an angle 2° with a light of wavelength 6980Å a) 0.2 mm b) 2×10 −5 mm c) 2×10 5 mm d) 2 mm 22. In the context of Doppler effect in light, the term ‘red shift’ signifies a) Decrease in frequency b) Increase in frequency c) Decrease in intensity d) Increase in intensity 23. The condition for obtaining secondary maxima in the diffraction pattern due to single slit is a) a sin sin θ = nλ b) a sin sin θ = (2n − 1) c) a sin sin θ = (2n − 1)λd) a sin sin θ = nλ 2 24. In a single slit diffraction experiment first minimum for red light (660 nm) coincides with first maximum of some other wavelength λ’. The value of λ' is a) 4400 Å b) 6600 Å c) 2000 Å d) 3500 Å 25. Two nicolprism are first crossed and then one of them is rotated through60°. The percentage of incident light transmitted is a) 1.25 b) 25.0 c) 37.5 d) 50 26. A narrow slit of width 2mm is illuminated by monochromatic light of wavelength 500nm. The distance between the first minima on either side on a screen at a distance of 1m is a) 5mm b) 0. 5mm c) 1mm d) 10mm 27. In a two slit experiment with monochromatic light fringes are obtained on a screen placed at some distance from the slits. If the screen is moved by 5×10 towards the slits, the change in fringe width is −2 m 3×10 . If separation between the slits is , the wavelength of light used is −5 m 10 −3 m a) 6000 Å b) 5000 Å c) 3000 Å d) 4500 Å 28. Light propagates 2cm distance in glass of refractive index 1.5 in timet . In the same time , light propagates 0 t 0 a distance of 2.25 cm in a medium. The refractive index of the medium is a) 4/3 b) 3/2 c) 8/3 d) None of these 29. If Young’s double slit experiment, is performed in water a) The fringe width will decrease b) The fringe width will increase c) The fringe width will remain unchanged d) There will be no fringe 30. Which of the following shows green house effect Page| 3
a) Ultraviolet rays b) Infrared rays c) X-rays d) None of these 31. At what angle should an unpolarised beam be incident on a crystal ofμ = 3, so that reflected beam is polarised? a) 45° b) 60° c) 90° d) 0° 32. In Young’s double slit experiment when wavelength used is 6000Å and the screen is 40 cm from the slits, the fringes are 0. 012 cm wide. What is the distance between the slits a) 0. 024 cm b) 2. 4 cm c) 0. 24 cm d) 0. 2 cm 33. Angular width of central maxima in the Fraunhoffter diffraction pattern of a slit is measured. The slit is illuminated by light of wavelength 6000 Å. When the slit is illuminated by light of another wavelength, the angular width decreases by 30%. The wavelength of this light will be a) 6000 Å b) 4200 Å c) 3000 Å d) 1800 Å 34. An electromagnetic wave propagating along north has its electric field vector upwards. Its magnetic field vector point towards a) North b) East c) West d) Downwards 35. A glass slab of thickness 8 cm contains the same number of waves as 10 cm of water when both are transverse by the same monochromatic light. If the refractive index of water is 4/3, then refractive index of glass is a) 5/4 b) 3/2 c) 5/3 d) 16/15 36. A beam of light of wavelength 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 the first dark fringes on either side of the central bright fringe is a) 1.2 cm b) 1.2 mm c) 2.4 cm d) 2.4 mm 37. Two polaroids are placed in the path of unpolarized beam of intensity I such that no light is emitted from 0 the second polaroid. If a third Polaroid whose polarization axis makes an angle θ with the polarization axis of first Polaroid, is placed between these polaroids, then the intensity of light emerging from the last Polaroid will be a) I 0 ( 8 )2θ b) I 0 ( 4 )2θ c) I 0 ( 2 )2θ d) I 0 θ 38. Two slits separated by a distance of 1 mm are illuminated with red light of wavelength 6.5× 10 m. the −7 interference fringes are observed on a screen place 1 m from the slits. The distance between the third dark fringe and the fifth bright fringe is equal to a) 0.65 mm b) 1.63 mm c) 3.25 mm d) 4.88 mm 39. Radiations of intensity 0. 5 W/m are striking a metal plate. The pressure on the plate is 2 a) 0. 166×10 −8N/m 2 b) 0. 332×10 −8N/m 2 c) 0. 111×10 −8N/m 2 d) 0. 083×10 −8N/m 2 40. The principle of superposition is basic to the phenomenon of a) Total internal reflection b) Interference c) Reflection d) Refraction 41. In Young’s double slit experiment distance between source is 1 mm and distance between the screen and source is 1m. If the fringe width on the screen is0.06 cm, then λ is Page| 4