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This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
The all India Radio, station at Vijayawala transmits its signals at `840 K C//s`. The wave length of the radio wave isA. `35.7 m`B. `357 m`C. `35.7 m`D. `3.57 m` |
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Answer» Correct Answer - B `lambda=(C )/(n)` |
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| 2. |
The displacement current was first postulated byA. AmpereB. MaxwellC. HertzD. Marconi |
| Answer» Correct Answer - B | |
| 3. |
The magnetic field In a travelling electromagnetic wave has a peak value of `20 n T ` The peak value of electric field strength is :A. `3 V//m`B. `6 V//m`C. `9 V//m`D. `12 V//m` |
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Answer» Correct Answer - B `vecE=vecBxxvecC` `|vecE|=|vecB|.|vecC|=20xx10^(-9)xx3xx10^(8)` `=6 V//m` |
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| 4. |
An electromagnetic radiation of frequency v, wavelength `lamda`, travelling with velocity c in air, enters a glass slab of refractive index `mu`. The frequency, wavelength and velocity of light in the glass slab will be respectively.A. `(v)/(mu),(lamda)/(mu)` and `(c)/(mu)`B. `v,(lamda)/(mu)` and `(c)/(mu)`C. `v,2lamda` and `(c)/(mu)`D. `(2v)/(mu),(lamda)/(mu)` and c |
| Answer» Correct Answer - B | |
| 5. |
A lamp emits monochromatic green light uniformly in all directions. The lamp is `3%` efficient in converting electrical power to electromagnetic waves and consumes `100 W` of power. The amplitude of the electric field associated with the electromagnetic. radiation at a distance of `10 m` from the lamp will beA. `1.34V//m`B. `2.68 V//m`C. `5.36 V//m`D. `9.37 V//m` |
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Answer» Correct Answer - A `S_(av)=(P)/(4piR^(2))=(1)/(2)epsilon_(0)cE_(0)^(2) :. E_(0)=sqrt((P)/(2piR^(2)epsilon_(0)c))` `sqrt((3)/(2xx3.14xx100xx8.85xx10^(-12)xx3xx10^(8)))=1.34V//m` |
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| 6. |
The magnetic field In a travelling electromagnetic wave has a peak value of `20 n T ` The peak value of electric field strength is :A. `6V//m`B. `9 V//m`C. `12 V//m`D. `3 V//m` |
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Answer» Correct Answer - A `B_(m)=(E_(m))/(C )` |
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| 7. |
Light with an energy flux of `18 W//cm^2` falls on a non-reflecting surface at normal incidence. If the surface has an area of `20 cm^2`, find the average force exerted on the surface during a `30` minute time span. |
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Answer» The total energy falling on the surface is `U=(18W//cm^(2))xx(20cm^(2))xx(30xx60)` `=6.48xx10^(6)J` Therefore, the total momentum dilivered (for complete absorption) is `p=(U)/(c)=(6.48xx10^(5)J)/(3xx10^(8)m//s)=2.16xx10^(-3)kg m//s` The average force exerted on the surface is `F=(p)/(t)=(2.16xx10^(-3))/(0.18xx14^(4))=1.2xx10^(-6)N` |
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| 8. |
The upper atmosphere layer is known asA. troposphereB. mesosphereC. ionosphereD. chromosphere |
| Answer» Correct Answer - C | |
| 9. |
Assertion: EM wave are transwers in nature. Reason: The electric and magnetic fields of an e.m. wave are perpendicular to each other also perpendicular to the direction of wave propagation.A. Statement-1 is true, statement-2, is true, statement-2 is a correct explanation for statement -1B. statement -1 is true, statement -2 is true, statement -2 is NOT a correct explanation for statement -1C. statement-1 is true , statement-2 is falseD. statement-1 is false, statement-2 is true |
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Answer» Correct Answer - A `lamda=(c//v)=1.5xx10^(-2)m` |
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| 10. |
In an electromagnetic wave in vacuum. The electrical and magnetic fields are `40piV//m` and `0.4xx10^(-7)T`. The poynting vectorA. `4.4 W m^(-1)`B. `0.44 W m^(-1)`C. `5.65 W m^(-1)`D. `4.0 W m^(-1)` |
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Answer» Correct Answer - D Poynting vector `=(B_(0)E_(0))/(mu_(0))` |
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| 11. |
The relative permeability of glass is `3//8` and the dielectric constant of glass is `8`. The refractive index of glass isA. `1.5`B. `1.1414`C. `1.732`D. `1.6` |
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Answer» Correct Answer - C `RI` of glass `=(C_(0))/(C )=sqrt((muepsilon)/(mu_(0)epsilon_(0)))=sqrt(mu_(r)epsilon_(r))` |
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| 12. |
The amplitude of the sinusodially oscillating electric field of a plane wave is `60V//m`. Then the amplitude of the magnetic field isA. `12xx10^(7)T`B. `6xx10^(7)T`C. `6xx10^(-7)T`D. `2xx10^(-7)T` |
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Answer» Correct Answer - D `C=(E_(0))/(B_(0))` |
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| 13. |
In an apparatus the electric field was found to oscillate with an amplitude of `18` `V//m`. The magnitude of the oscillating magnrtic field will beA. `6xx10^(-8)T`B. `4.23xx10^(-8)T`C. `9xx10^(-8)T`D. `7.0xx10^(-8)T` |
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Answer» Correct Answer - B `C=(E)/(B)` |
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| 14. |
Can electric field lines of force form closed loops ? Give reason for your answer.A. (`i`) onlyB. (`ii`) onlyC. (`iii`) onlyD. (`iv`) only |
| Answer» Correct Answer - A | |
| 15. |
Statement-1 : A changing electric field produces a magnetic field Statement-2: A changing magnetic field produces an electric field.A. Statement-1 is true, statement-2, is true, statement-2 is a correct explanation for statement -1B. statement -1 is true, statement -2 is true, statement -2 is NOT a correct explanation for statement -1C. statement-1 is true , statement-2 is falseD. statement-1 is false, statement-2 is true |
| Answer» Correct Answer - B | |
| 16. |
Out of the above four equations, the equations which do not contain source field are-A. (`i`) and (`ii`)B. (`ii`) onlyC. all of fourD. (`iii`) only |
| Answer» Correct Answer - B | |
| 17. |
An electruc field of `300V//m` is confined to a circular area `10 cm` in diameter. If the field is increasing at the rate of `20V//m-s`, the magnitude of magnetic field at a point `15cm` from the centre of the circle will be-A. `1.85xx10^(-15)T`B. `1.85xx10^(-16)T`C. `1.85xx10^(-17)T`D. `1.85xx10^(-18)T` |
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Answer» Correct Answer - D `B=(mu_(0)epsilon_(0))/(2piR)((pid^(2))/(4))(dE)/(dt)` `=(2xx10^(-7)xx8.85xx10^(-12)xx3.14xx0.01x20)/(4xx0.15)` `=1.85xx10^(-18)T` |
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| 18. |
A plane electromagnetic wave of frequency `25 Mhz` travels in free space along the x-direction. At a particular point in space and time, `E= (6.3 j) V//m`. What is `B` at this point?A. `4.2xx10^(-8)hatk T`B. `2.1xx10^(-8)hatk T`C. `18.9xx10^(8)hatk T`D. `2.1xx10^(8)hatk T` |
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Answer» Correct Answer - B `B=(E)/(C )` |
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| 19. |
A plane electromagnetic wave of frequency `25 Mhz` travels in free space along the x-direction. At a particular point in space and time, `E= (6.3 j) V//m`. What is `B` at this point? |
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Answer» Using Eq. (8.10), the magnitude of B is `B=(E)/(c)` `=(6.3 V//m)/(3xx10^(8)m//s)=2.1xx10^(-8)T` To find the direction, we note that E is along y-direction and the wave propagate along x-axis. Therefore B should be in a direction perpendicular to both x--and y-axes. Using vector algebra, `ExxB` should be along x-direction since, `(+hatj)xx(+hatK)=hati`, B is along the z-direction Thus, `B=2.1xx10^(-8)kT` |
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| 20. |
A plane `E.M.` wave of frequency `40 MHz` travels along `X`-axis. At same point at same instant, the electric field `E` has maximum value of `750 N//C` in `Y`- direction. The magnitude and direction of magnetic field isA. `2.5 muT` along `X-"axis"`B. `2.5 muT` along `Y-"axis"`C. `2.5 muT` along `Z-"axis"`D. `5 muT` along `Z-"axis"` |
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Answer» Correct Answer - C `B=(E)/(C )` |
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| 21. |
The wave emitted by any atom or molecule must have some finitetotal length which is known as the choherence length. For sodium light, this length is `2.4 cm`. The number of oscillations in this length will be Given `lambda=5900A^(@)`A. `4.068xx10^(5)Hz`B. `4.068xx10^(4)Hz`C. `4.068xx10^(6)Hz`D. `4.068xx10^(8)Hz` |
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Answer» Correct Answer - B No. of ocillations in this length `=(l)/(lambda)` |
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| 22. |
If `E` and `B` represent electric and magnetic field vectors of the electromagnetic wave, the direction of propagation of eletromagnetic wave is along.A. `vecE`B. `vecB`C. `vecBxxvecE`D. `vecExxvecB` |
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Answer» Correct Answer - D A changing electric field produces a changing magnetic field and vice versa which gives rise to a transverse wave known as electromagnetic wave. The time varying electric and magnetic fields are mutually perpendicular to each and also perpendicular to the direction of propagation of this wave. The electrion vector is responsible for the optical effects of an `EM` wave and is called the light vector The direction of propagation of electromagnetic wave is perependicular to both electric field vector `(vecE)` and `(vecB)` magnetic field vector `B` i.e, inthe direction of `vecExxvecB` Here electromagnetic wave is along the `z`-direction which is given by the cross product of `E` and `B` |
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| 23. |
The electric and magnetic field of an electromagnetic wave isA. in phase and parallel to each otherB. in opposite phase and perpendicular to each otherC. in opposite phase and parallel to each otherD. in phase and perpendicular to each other. |
| Answer» Correct Answer - D | |
| 24. |
Which has the longest wavelengthA. infrared lightB. ultraviolet lightC. radio-wavesD. X-rays |
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Answer» Correct Answer - C Comparing the given equation `E_(y)=2.5(N)/(C)cos[(2pixx10^(6)(rad)/(sec))t-(pixx10^(-2)(rad)/(sec))x]` With the standard equation `E_(y)=E_(0)cos(omegat-kx)` we get `omega=2pif=2pixx10^(6)` `:. f=10^(6)Hz` Moreover, we know that `(2pi)/(lamda)=k=pixx10^(-2)m^(-1)implieslamda=200m` |
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| 25. |
Hertz produced electromagnetic wave by usingA. L C R circuitB. C R circuitC. L C circuitD. none of the above |
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Answer» Correct Answer - C Velocity of light waves in material is `v=nlamda` ..(i) Refractive index of material is `mu=(c)/(v)` ..(ii) Where `c` is speed of light in vacuum or air. or `mu=(c)/(nlamda)` ..(iii) Given, `n=2xx10^(14)Hz` `lamda=5000A=5000xx10^(-10)m` `c=3xx10^(8) m//s` Hence, from Eq. (iii) we get `mu=(3xx10^(8))/(2xx10^(14)xx5000xx10^(-10))=3.00` |
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| 26. |
The frequency of visibile light is of the order ofA. `10^(15)Hz`B. `10^(10)Hz`C. `10^(6)Hz`D. `10^(4)Hz` |
| Answer» Correct Answer - A | |
| 27. |
An accelerated electric charge emitsA. `beta`- raysB. `gamma`- raysC. e.m. wavesD. none of the above |
| Answer» Correct Answer - C | |
| 28. |
Which of the following wavelenght falls in `X`-rays region?A. `1A^(0)`B. `10^(-2)A^(0)`C. `10^(-3)A^(0)`D. `10^(-4)A^(0)` |
| Answer» Correct Answer - A | |
| 29. |
Electromagnetic waves in nature areA. longitudinalB. longitudinal stationaryC. transverseD. transverse-stationary |
| Answer» Correct Answer - C | |
| 30. |
The frequencies of `X`-rays, `gamma`-rays and ultraviolet rays are respectively `a, b and c` .ThenA. `a lt b`, `b lt c`B. `a gt b`, `b gt c`C. `a gt b`, `b lt c`D. `a lt b`,`b gt c` |
| Answer» Correct Answer - D | |
| 31. |
The nature of electromagnetic wave is-A. longitudinalB. longitudinal stationaryC. transverseD. transverse stationary |
| Answer» Correct Answer - C | |
| 32. |
The electric and magnetic field of an electromagnetic wave isA. mutually perpendicular to each otherB. all parallelC. at `30^(@)` to each otherD. at `60^(@)` to each other |
| Answer» Correct Answer - A | |
| 33. |
The waves related to telecommuni-cation are-A. infra redB. visible lightC. microwavesD. ultraviolet rays |
| Answer» Correct Answer - C | |
| 34. |
Select wrong statement from the following - Electomagnetic wavesA. are transverseB. travels free space at the speed of lightC. are produced by accelerating chargesD. travel with the same speed in all media |
| Answer» Correct Answer - D | |
| 35. |
Select wrong statement from the following - Electomagnetic wavesA. are transverseB. travel with same speed in all mediaC. travel with the speed of lightD. are produced by accelerating charge. |
| Answer» Correct Answer - B | |
| 36. |
A capcitor is connected in an electric circuit with an open key, immediately after pressing the key, the current in the circuit is-A. zeroB. maximumC. any transient valueD. depends on capacitor used |
| Answer» Correct Answer - B | |
| 37. |
The electromagnetic waves do not transportA. energyB. chargeC. momentumD. information |
| Answer» Correct Answer - B | |
| 38. |
The magnetic field between the circulate plates of radius `12cm` separted by distance of `4mm` of a parallel plate capacitor of capacitance `100 pF`. Along the axis of plates having conduction current of `0.15 A` isA. zeroB. `1.5 T`C. `15 T`D. `0.15 T` |
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Answer» Correct Answer - A `B=(mu_(0)I_(d)r)/(2piR^(2))`, `r=0` |
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| 39. |
Statement 1 : Electromagnetic waves exert pressure called radiation pressure. Statement-2 : This is because they carry energy.A. Statement-1 is true, statement-2, is true, statement-2 is a correct explanation for statement -1B. statement -1 is true, statement -2 is true, statement -2 is NOT a correct explanation for statement -1C. statement-1 is true , statement-2 is falseD. statement-1 is false, statement-2 is true |
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Answer» Correct Answer - B `B_(0)=(E_(0)//c)=1.6xx10^(-7)T` |
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| 40. |
The electric field part of an electromagnetic wave in a medium is represented by `E_(x)=0,` `E_(y)=2.5(N)/(C) cos[(2pixx10^(6)(rad)/(m))t-(pixx10^(-2)(rad)/(s))x]` `E_(z)=0`. The wave isA. moving along y direction with frequency `2pixx10^(6)Hz` and wavelength 200 m.B. moving along x direction with frequency `10^(6)Hz` and wavelength 100 m.C. moving along x direction with frequency `10^(6)Hz` and wavelength 200 m.D. moving along `-x` direction with frequency `10^(6)Hz` and wavelength 200 m. |
| Answer» Correct Answer - C | |
| 41. |
The velocity of electromagnetic radiatior in a medium of permittivity `epsilon_(0)` and permeability `mu_(0)` is given byA. `sqrt((epsilon_(0))/(mu_(0)))`B. `sqrt(mu_(0)epsilon_(0))`C. `(1)/(sqrt(mu_(0)epsilon_(0)))`D. `sqrt((mu_(0))/(epsilon_(0)))` |
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Answer» Correct Answer - C Velocity of electromagnetic radiation is the velocity of light (c), is `(1)/(sqrt(mu_(0)epsilon_(0)))` Where `mu_(0)` is the permeability and `epsilon_(0)` is the permittivity of free space. |
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| 42. |
Write the mathmatical equation of Ampere-maxwell law. |
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Answer» Mathematical equation of ampere-maxwell law. `ointB.dl=mu_(0)i_(c)+mu_(0)epsilon_(0)(dPhi_(E))/(dt)` |
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| 43. |
To which part of the electromagnetic spectrum does a wave of frequency `5xx10^(11)` Hz belong? |
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Answer» Correct Answer - Microwaves Microwaves |
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| 44. |
Which rays are not the portion of electro-magnetic spectrum?A. x-raysB. microwavesC. `alpha`-raysD. radiowaves. |
| Answer» Correct Answer - C | |
| 45. |
Identify the constituent radiations of electromagnetic spectrum which (1). Is absorbed by ozone layer in the atmosphere (2). Is produced by bombarding a metal target by high speed electrons (3). Is used in satellite communication (4). has wavelength range between 400 nm to 700 nm. |
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Answer» (a). Ultraviolet violet rays (b). X-rays (c). Microwaves (d). Visible rays. |
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| 46. |
Heat radiations propagate with the speed ofA. `alpha`-raysB. `beta`-raysC. light wavesD. sound waves |
| Answer» Correct Answer - C | |
| 47. |
Infrared spectrum lies betweenA. radio wave and microwave region.B. microwave and visible regionC. visible and ultra-violet regionD. ultra violet and X-ray |
| Answer» Correct Answer - B | |
| 48. |
The electromagnetic radiations are in descending order of wavelength in the following sequenceA. infra-red waves, radio waves X-rays, visible light raysB. radio-waves, infra-red waves, visible, X-raysC. radio waves, visible light, infra-red waves, X-raysD. X-rays, visible light, infra-red wave, radiowaves |
| Answer» Correct Answer - B | |
| 49. |
Which of the following statements is not correct?A. photographic plates are sensitive to infrared raysB. photographic plates are sensitive to ultraviolet raysC. Infra-red-rays are invisible but can cast shadows like visible lightD. infrared photons have more energy then phtotons of visible light |
| Answer» Correct Answer - D | |
| 50. |
Energy stored in electromagnetic osicllations is in the form ofA. electrical energyB. magnetic energyC. both `1` and `2`D. neither of the above |
| Answer» Correct Answer - C | |