InterviewSolution
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InterviewSolution
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Light of wavelength `6328 Å` is incident normally on a slit having a width of `0.2 mm`. The distance of the screen from the slit is `0.9 m`. The angular width of the central maximum isA. `0.09^(@)`B. `0.72^(@)`C. `0.18^(@)`D. `0.36^(@)` |
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Answer» Correct Answer - D Angular width of central maximum `theta_(0)=(2lambda)/a=(2xx6328xx10^(-10))/(0.2xx10^(-3))=6.328xx10^(-3) rad` `=[(6.328xx10^(-3))xx180/pi]^(@)=0.36^(@)` |
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| 2. |
A single slit of width `0.20 mm` is illuminated with light of wavelength `500 nm`. The observing screen is placed `80 cm` from the slit. The width of the central bright fringe will beA. `1 mm`B. `2 mm`C. `4 mm`D. `5 mm` |
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Answer» Correct Answer - C Width of central bright fringe`=(2Dlambda)/a` `=(2xx0.8xx500xx10^(-9))/(0.2xx10^(-3))=4xx10^(-3) m=4 mm` |
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| 3. |
A parallel beam of sodium light of wavelength `6000 Å` is incident on a thin glass plate of `mu=1.5`, such that the angle of refraction in the plate is `60^(@)`. The smallest thickness of the plate which will make it appear dark by reflected light isA. `40 Å`B. `4 Å`C. `400 Å`D. `4000 Å` |
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Answer» Correct Answer - D For reflected light `2 mut cos r-lambda/2=(2n+1)lambda/2` `2 mu t cos r=(2n+1)lambda/2+lambda/2, n=0` `2xx1.5xxt cos 60^(@)=lambda=6000` `t=6000/1.5=4000 Å` |
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| 4. |
Light of wavelength `5000 Å` is travelling in air. A thin glass plate (mu=1.5) of thickness `1 mm` is placed in the path of light. The change in phase of light isA. zeroB. `pi//2`C. `pi`D. `(3pi)//2` |
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Answer» Correct Answer - A `Deltax=(mu-1)t=(1.5-1)xx10^(-3)=5xx10^(-4)m` `phi=(2pi)/lambda Deltax=(2pi)/(5xx10^(-7))xx5xx10^(-4)=2000pi` `2000 pi i.e. 0` |
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| 5. |
A thin mica sheet of thickness `2xx10^-6m` and refractive index `(mu=1.5)` is introduced in the path of the first wave. The wavelength of the wave used is `5000Å`. The central bright maximum will shiftA. `2` fringes upwardB. `2` fringes downwardC. `10` fringes upwardD. none of these |
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Answer» Correct Answer - C Shift/(Fringe width)`=y_(0)/beta=((mu-1)tD/d)/((Dlambda)/d)=((mu-1)t)/lambda` `=((1.5-1)xx2xx10^(-6))/(5xx10^(-7))=10` `10` fringes upward. |
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| 6. |
In the ideal double-slit experiment, when a glass-plate (refractive index 1.5) of thickness t is introduced in the path of one of the interfering beams (wavelength `lambda`), the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass-plate isA. `2lambda`B. `2lambda//3`C. `lambda//3`D. `lambda` |
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Answer» Correct Answer - A `phi=(2pi)/lambdaDeltax=(2pi)/lambda(mu-1)t` `phi=0, 2pi, 4pi, …` `2pi=(2pi)/lambda(1.5-1)t implies t=2lambda` |
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| 7. |
When a transparent parallel plate of uniform thickness `t` and refractive index `mu` is interposed normally in the path of a beam of light, the optical path isA. increased by `mut`B. decreased by `mut`C. decreased by `(mu-1)t`D. increased by `(mu-1)t` |
| Answer» Correct Answer - D | |
| 8. |
A screen is placed 50cm from a single slit, which is illuminated with 6000Å light. If distance between the first and third minima in the diffraction pattern is 3.0 mm, what is the width of the slit? |
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Answer» `D=50 cm, lambda=600 nm` `y_(3)-y_(1)=(3Dlambda)/a=(Dlambda)/a=(2Dlambda)/a` `3xx10^(-3)=(2xx0.5xx600xx10^(-9))/a` `a=200xx10^(-6) m=0.2 mm` |
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| 9. |
Which one of the following phenomena is not explained by Huygens construction of wavefront?A. refractionB. reflectionC. diffractionD. origin of spectra |
| Answer» Correct Answer - D | |
| 10. |
The phenomenon of interference is shown byA. longitudinal mechanical waves onlyB. transverse machanical transverse waves onlyC. non-mechanical transverse waves onlyD. all the above types of waves |
| Answer» Correct Answer - D | |
| 11. |
In the interference pattern, energy isA. created at the positions of maximaB. destroyed at the positions of maxmaC. conserved but is redistributedD. not conserved |
| Answer» Correct Answer - C | |
| 12. |
A monochromatic light of `lambda=500 nm` is incident on two identical slits separated by a distance of `5xx10^(-4)m`. The interference pattern is seen on a screen placed at a distance of `1 m` from the plane of slits. A thin glass plate of thickness `1.5xx10^(-6)m` and refractive index `mu=1.5` is placed between one of the slits and the screen. Find the intensity at the centre of the screen if the intensity is `I_(0)` in the absence of the plate. Also find the lateral shift of the central maxima and number of fringes crossed through centre. |
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Answer» `lambda=500 nm, d=5xx10^(-4) m, D=1 m` `t=1.5xx10^(-6)m, mu=1.5` Path difference due to plate, `Deltax=(mu-1)t=(1.5-1)xx1.5xx10^(-6)=0.75xx10^(-6)m` `phi=(2pi)/lambda Deltax=(2pi)/(500xx10^(-9))xx0.75xx10^(-6)=3pi` `I_(R)=I_(0) cos^(2) (phi//2)=I_(0) cos^(2)(1.5 pi)=0` Lateral shift `y_(0)=((mu-1)tD)/d=(0.75xx10^(-6)xx1)/(5xx10^(-4))` `=0.15xx10^(-2)m=1.5 mm` number of fringes crossing the centre `y_(0)/beta=(((mu-1)tD)/d)/((Dlambda)/d)=((mu-1)t)/lambda=(0.75xx10^(-6))/(500xx10^(-9))=1.5` |
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| 13. |
When light is refracted into a mediumA. its wavelength and frequency remain unchangedB. its wavelength increases but frequency remain unchangedC. its wavelength decreases but frequency remain unchangedD. its wavelength anf frequency both decrease |
| Answer» Correct Answer - C | |
| 14. |
The contrast in the fringes in an interference pattern depends onA. fringe widthB. wavelengthC. intensity ratio of the sourcesD. distance between the slits |
| Answer» Correct Answer - C | |
| 15. |
The equation of a light wave i written as `y=Asin(kx-omegat)`. Here y representsA. displacement of either particlesB. pressure in the mediumC. density of the mediumD. electric field or magnetic field |
| Answer» Correct Answer - D | |
| 16. |
The speed of light dependsA. on elasticity of the medium onlyB. on inertia of the medium onlyC. on elasticity as well as inertiaD. neither on elasticity nor on inertia |
| Answer» Correct Answer - D | |
| 17. |
Lifgt isA. wave phenomenonB. particle phenomenonC. both particle and wave phenomenonD. none |
| Answer» Correct Answer - C | |
| 18. |
When sunlight is incident on water surface at glacing angle of `37^(@)`, the reflected light is found to be completely plane-polarised. Determine (a) the refractive index of water and (b) angle of refraction. |
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Answer» (a) `mu=tanp=tan 53^(@)=4//3` (b) `i+r=90^(@)implies p+r=90^(@)implies53+r=90` `r=37^(@)` |
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| 19. |
When exposed to sunlight, thin films of oil on water often exhibit brilliant colours due to the phenomenon ofA. disperion of lightB. interference of lightC. absorption of lightD. scattering of light |
| Answer» Correct Answer - B | |
| 20. |
When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light isA. polarisedB. of longer wavelengthC. of shorter wavelengthD. of high intensity |
| Answer» Correct Answer - A | |
| 21. |
If the ratio of amounts of scattering of two light waves is 1:4, the ratio of their wavelength isA. `1:2`B. `sqrt(2):1`C. `1:sqrt(2)`D. `1:1` |
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Answer» Correct Answer - B Scattering `prop1/lambda^(4)` `(("scattering")_(1))/(("scattering")_(2))=(lambda_(2)/lambda_(1))^(4)` `1/4=(lambda_(2)/lambda_(1))^(4) implies lambda_(2)/lambda_(1)=1/sqrt(2) implies lambda_(1)/lambda_(2)=sqrt(2)/1` |
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| 22. |
Check the correct statements on scattering of light `S1`: Rayleigh scattering is responsible for the bluish appearance of sky `S2`: Rayleigh scattering is proportional to `1//lambda^(4)` when the size of the scatterer is much less than `lambda` `S3`: Clouds having droplets of water (large scattering objects) scatter all wavelengths are almost equal and so are generally white `S4`: The sun looks reddish at sunset and sunrise due to Rayleigh scatteringA. S1 onlyB. S1 and S2C. S2 and S3D. S1, S2, S3 and S4 |
| Answer» Correct Answer - D | |
| 23. |
An astronaut in a spsceship sees the outer space asA. whiteB. blackC. blueD. red |
| Answer» Correct Answer - B | |
| 24. |
The angle of incidence at which reflected light is totally polarized for reflection from air to glass (refractive index n),A. `sin^(-1)(n)`B. `sin^(-1)(1/n)`C. `tan^(-1)(1/n)`D. `tan^(-1)(n)` |
| Answer» Correct Answer - D | |
| 25. |
The penetration of light into the region of geometrical shadow is calledA. polarisationB. interferenceC. diffractionD. refraction |
| Answer» Correct Answer - C | |
| 26. |
Choose the correct option: (i) A surface on which the wave disturbance in same phase at all points is called a wavefront. (ii) The direction of a wave at a point is perpendicular to the wavefront through that point. (iii) The wavefronts of a wave originating from a point source is spherical. The wavefronts for a wave going along a fixed direction are planes perpendicular to that direction.A. (i), (ii)B. (ii), (iii), (iv)C. (i), (ii), (iii)D. all |
| Answer» Correct Answer - D | |
| 27. |
Choose the correct option:A. Light of single wavelength is called monochromatic light.B. The best monochromatic light are LASERs in which the spread of wavelength is very small but not zero.C. The wavelength of visible light is around 380-780 nm. The obstacles or openings encountered in normal situations are generally of the order of mm. As wavelength is several is thousands times smaller than the usual obstacles or openings. The diffraction (bending of light) is almost neglible and light waves propagate in straight lines and cast shadows of obstacles. This is the geometrical optics approximation. By the above analysis rectilinear propagation of light can be explained.D. All options are correct. |
| Answer» Correct Answer - D | |
| 28. |
The velocity of light in diamond, glass and water decreases in the following orderA. watergt glassgt diamondB. diamondgt glassgt waterC. diamondgt watergt glassD. watergt diamondgt glass |
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Answer» Correct Answer - A `v prop 1//mu` `mu_(omega)=4//3=1.33, mu_(g)=3//2=1.5, mu_(d)=2.4` |
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| 29. |
Ray optics is valid when characteristic dimensions areA. of the same order as the wavelength of lightB. much smaller than the wavelength of lightC. much large than the wavelength of lightD. of the order of `1 mm` |
| Answer» Correct Answer - C | |
| 30. |
Light appears to travel in straight lines sinceA. it is not absorbed by the atmosphereB. it is reflected by the atmosphereC. its wavelength is very smallD. its velocity is very large |
| Answer» Correct Answer - C | |
| 31. |
White light may be considered to be mixture of waves of `lambda` ranging between `3900 Å` and `7800 Å`. An oil film of thickness `10,000 Å` is examined normally by the reflected light. If `mu=1.4`, then the film appears bright forA. `4000 Å, 4667 Å, 5600 Å, 7000 Å`B. `4308 Å, 5091 Å, 6222 Å`C. `4000 Å, 5091 Å, 5600 Å`D. `4667 Å, 6222 Å, 7000 Å` |
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Answer» Correct Answer - B `2 mut-lambda/2=nlambda` `2mut=(n+1//2)lambda` `lambda=(2mut)/(n+1//2)=(2xx1.4xx10000)/(n+1//2)=28000/(n+1//2)` `n=0, lambda=56000 Å` `n=1, lambda=15333 Å` `n=2, lambda=11200 Å` `n=3, lambda=8000 Å` `n=4, lambda=6222 Å` `n=5, lambda=5091 Å` `n=6, lambda=4308 Å` ` lambda=4308 Å, 5091 Å, 6222 Å` |
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| 32. |
Diffraction effects are easier to notice in the case of sound waves than in the case of light waves becauseA. sound waves are longitudinalB. sound is perceived by the carC. sound waves are mechanical wavesD. sound waves are of longer wavelength |
| Answer» Correct Answer - D | |
| 33. |
Yellow light is used in a single slit diffraction experiment with slit width of 0.6 mm. If yellow light is replaced by X-rays, then the observed pattern will reveal,A. that the central maxima is narrowerB. no diffraction patternC. more number of fringesD. less number of fringes |
| Answer» Correct Answer - A | |
| 34. |
Two sources of intensity `I` and 4I are used in an interference experiment. Find the intensity at a point where the waves from two sources superimpose with a phase difference of (a) zero, (b) `pi//2`, (c ) `pi` and (d) ratio of maximum and minimum intensity. |
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Answer» `I_(1)=I, I_(2)=4I` `I_(R)=I_(1)+I_(2)+2sqrt(I_(1)I_(2)) cos phi` (a) `phi=0, I_(R)=I+4I+2sqrt(I.4I) cos 0=9I=I_(max)` (b) `phi=pi/2, I_(R)=I+4I+2sqrt(I.4I) cos(pi//2)=5 I` (c ) `phi=pi, I_(R)=I+4I+2sqrt(I.4I) cos(pi)=I=I_(min)` (d) `I_(max)/I_(min)=(9I)/I=9` OR `I_(max)/I_(min)= ((sqrt(I_(1))+sqrt(I_(2)))/(sqrt(I_(1))-sqrt(I_(2))))^(2)=((sqrt(I)+sqrt(4I))/(sqrt(I)-sqrt(4I)))^(2)=9` |
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| 35. |
Two point sources X and Y emit waves of same frequency and speed but Y lags in phase behind X by `2 pid` radian. If there is a maximum in direction D, the distance XO using n as an integer is given by A. `lambda/2(n-l)`B. `lambda(n+l)`C. `lambda/2(n+l)`D. `lambda(n-l)` |
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Answer» Correct Answer - B `phi=(2pi)/lambda Deltax-2pil` `2pin=(2pi)/lambda(OX)-2pil` `OX=lambda(n+l)` |
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| 36. |
Which of the following sources gives best mionochromatic light?A. A candleB. A bulbC. A mercury tubeD. A laser |
| Answer» Correct Answer - D | |
| 37. |
Two sources of light are said to be coherent if the waves produced by them have the sameA. wavelengthB. amplitudeC. wavelength and amplitudeD. wavelength and a constant phase difference |
| Answer» Correct Answer - D | |
| 38. |
A laser beam is used for carrying our surgery because itA. many wavelengthB. un-coordinated wavelengthC. coordinated waves of exactly the same wavelengthD. divergent beams |
| Answer» Correct Answer - C | |