12th Physics , Chapter-6 ( ELECTROMAGNETIC WAVES )
(1) What feature of electromagnetic waves led Maxwell to conclude that light itself is electromagnetic wave:
(a) travelling in vacuum
(b) travelling in st. line
(c) diffracted by an obstacle
(d) None of these
Answer
(2) Which of the following has smallest wavelength :
(a) yellow rays
(b) X-rays
(c) a-rays
(d) Gamma-rays
Answer
(3) Displacement current is the same as :
(a) rms current
(b) peak current.
(c) conduction current
(d) none of these
Answer
(4) Displacement current is measured in:
(a) A
(b) C
(c) Cs
(d) Vm-¹
Answer
(5) Who discovered displacement current ?
(a) Hertz
(b) Maxwell
(c) Marconi
(d) None of these
Answer
(6) The direction of electromagnetic waves is given by :
(a) E. B.
(b) Ex B
(c) E
(d) EB
Answer
(7) Name the law which states that a varying electric field produces a magnetic field:
(a) Biot-Savart law
(b) Faraday’s law
(c) Modified Ampere’s law
(d) None of these
Answer
(8) The phase difference between electromagnetic wave is electric and magnetic fields in an
(a) 0
(b) π/2
(с) 2
(d) anything.
Answer
(9) Electromagnetic waves can be polarised by
(a) a lens
(b) a mirror
(c) a polaroid
(d) a prism
Answer
(10) How are X-rays produced:
(a) High energy electrons are stopped suddenly by a metal of high atomic no
(b) Proton strikes with radioactive element.
(c) electrons strikes with low atomic no, element
(d) None of these
Answer
(11) Which part of electromagnetic spectrum is used in radar system?
(a) Ultraviolet
(b) Infra red
(c) Radio waves
(d) X rays.
Answer
(12) Why are microwaves used in RADAR:
(a) They can be beamed in a particular direction.
(b) Have smaller wavelength of few mm.
(c) They are not diffracted
(d) All the above
Answer
(13) Name the electromagnetic radiation used for viewing objects through haze and fog:
(a) Infrared rays
(b) X-rays
(c) Microwaves
(d) None
Answer
(14) In electromagnetic wave spectrm, the most energetic wave is:
(a) X-ray
(b) UV-ray
(c) radio wave
(d) Gamma Ray
Answer
(15) Which of the following will be deflected in electric field:
(a) X-rays
(b) y-rays
(c) Cathode rays
(d) u-v-rays
Answer
(16) Name the law which states that a varying electric field produces amagnetic field:
(a) Biot-Savart law
(b) Faraday’s law
(c) Modified Ampere’s law
(d) None of these
Answer
(17) The phase difference between electromagnetic wave is electric and magnetic fields in an
(a) 0
(b) π/2
(с) л
(d) anything.
Answer
(18) Electromagnetic waves can be polarised by
(a) a lens
(b) a mirror
(c) a polaroid
(d) a prism
Answer
(19) Velocity of light is equal to:
(a) νεομο
(b) E_{0}/mu_{0}
(c) r0 co
(d) sqrt(epsilon_{0\mu})
Answer
(20)Electromagnetic wave is
(a) Transverse
(b) Longitudinal
(c) Mechanical
(d) Elastic waves
Answer
(21) What is the speed of an electromagnetic wave?
(a) 3 * 10 ^ 5 * m /
(b) 3*108m/s
(c) 3 x 106 m/s
(d) None
Answer
(22)The wavelength of an electromagnetic wave is doubled. What willhappen to its energy :
(a) Energy becomes half
(b) Energy is also doubled
(c) No effect
(d)none
Answer
(23) Write an expression for speed of electromagnetic waves in free space :
(a) C = 1/(sqrt(mu_{0}*epsilon_{0}))
(b) 3 * 1 m/s
(c) C = με
(b) C = sqrt(mu_{0}*epsilon_{0}))
Answer
(24) What is common among different types of electromagnetic radiations
(a) Speed
(b) Wavelength
(c) Frequency
(d)none
Answer
(25) What oscillates in an electromagnetic wave:
(a) The electric and magnetic field vectors
(b) The particles of the medium
(c) Only electric field vector
(d) None of these
Answer
(26) What is the main difference between X-ray and y-ray on the basis ofwavelength:
(a) X-ray has greater wavelength than y-rays.
(b) y-ray has greater wavelength than X-ray.
(c) both have same wavelength.
(d) None of these
Answer
(27)what are micro –waves :
(a) Electromagnetic waves of wavelength of few mm.
(b) Radio wave of frequency greater than that of radio waves.
(c) Both (a) and (b)
(d) None of these
Answer
(28) Name the law which states that a verifying electric field product a magnetic filed :
(a) Biot-Savart law
(b) faraday’s law
(c) modifies Amper’s law
(d) None Of these
Answer
(29) What oscillates in an electromagnetic wave:
(a) The electric and magnetic field vectors
(b) The particles of the medium
(c) Only electric field vector
(d) None of these
Answer
(30) What is the main difference between X-ray and y-ray on the basis ofwavelength:
(a) X-ray has greater wavelength than y-rays.
(b) y-ray has greater wavelength than X-ray.
(c) both have same wavelength.
(d) None of these
Answer
(31) What are micro-waves:
(a) Electromagnetic waves of wavelength of few mm.
(b) Radio wave of frequency greater than that of radio waves.
(c) Both (a) and (b)
(d) None of these
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