NEET AIPMT Physics Chapter Wise Solutions – Electromagnetic Waves
1. The energy of the em waves is of the order of 15 keV. To which part of the spectrum does it belong? (AIPMT 2015)
(a) Ultraviolet rays
(d) Infra-red rays
2. A radiation of energy ‘E’ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (C = Velocity of light)
3. Light with an energy flux of 25 × 104 W m-2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm the average force exerted on the surface is (AIPMT 2014)
(a) 1.25 × 106 N
(b) 2.50 × 106 N
(c) 1.20 × 10-6 N
(d) 3.0 × 10-6 N
4. The condition under which a microwave oven ; heats up a food item containing water molecules most efficiently is (NEET 2013)
(a) Microwaves are heat waves, so always produce heating.
(b) Infra-red waves produce heating in a microwave oven.
(c) The frequency of the microwaves must match the resonant frequency of the water molecules.
(d) The frequency of the microwaves has no relation with natural frequency of water molecules.
5. An electromagnetic wave of frequency u = 3.0 MHz passes from vacuum into a dielectric medium with relative permittivity
∈ = 4.0. Then (Karnataka NEET 2013)
(a) Wavelength is doubled and frequency becomes half.
(b) Wavelength is halved and frequency remains unchanged.
(c) Wavelength and frequency both remain unchanged.
(d) Wavelength is doubled and frequency unchanged.
6.The electric field associated with an’em wave in vacuum is given by E = i 40 cos (kz – 6 × 108 t) where E, z and t are in volt/m, meter and seconds respectively. The value of wave vector k is (Prelims 2012)
(a) 2 m-1
(b) 0.5 m-1
(c) 6 m-1
(d) 3 m-1
7. The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagating in vacuum is equal to (Mains 2012)
(a) the speed of light in vacuum
(b) reciprocal of speed of light in vacuum
(c) the ratio of magnetic permeability to the electric susceptibility of vacuum
8. The electric and the magnetic field, associated with an e.m. wave, propagating along the +z-axis, can be represented by (prelims 2011)
9. The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is (Prelims 2011)
(a) microwave, infrared, ultraviolet, gamma rays
(b) gamma rays, ultraviolet, infrared, microwaves
(c) microwaves, gamma rays, infrared, ultraviolet
(d) infrared, microwave, ultraviolet, gamma rays
10. Which of the following statement is false for the properties of electromagnetic waves? (Prelims 2010)
(a) Both electric and magnetic field vectors attain the maxima and minima at the same place and same time.
(b) The energy in electromagnetic wave is divided equally between electric and magnetic vectors.
(c) Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave.
(d) These waves do not require any material medium for propagation.
11. The electric field of an electromagnetic wave in free space is given by E = 10 cos (107 t + k x)j V/m, where t and x are in seconds and metres respectively. It can be inferred that (Mains 2010)
(1) the wavelength λ is 188.4 m.
(2) the wave number k is 0.33 rad/m.
(3) the wave amplitude is 10 V/m.
(4) the wave is propagating along +x direction.
Which one of the following pairs of statements is correct?
(a) (3) and (4)
(b) (1) and (2)
(c) (2) and (3)
12. The electric field part of an electromagnetic wave in a medium is represented
13. The velocity of electromagnetic radiation in a medium of permittivity e0 and permeability p0 is given by (prelims 2008)
14. The electric and magnetic field of an electromagnetic wave are (2007, 1994)
(a) in opposite phase and perpendicular to each other
(b) in opposite phase and parallel to each other
(c) in phase and perpendicular to each other
(d) in phase and parallel to each other.
16. We consider the radiation emitted by the human body. Which one of the following statements is true ? (2003)
(a) The radiation emitted is in the infra-red region
(b) The radiation is emitted only during the day
(c) The radiation is emitted during the summers and absorbed during the winters
(d) The radiation emitted lies in the ultraviolet region and hence is not visible
17. Which of the following rays are not electromagnetic waves ? (2003)
(d) heat rays
18. The velocity of electromagnetic wave is parallel to (2002)
19. What is the cause of Green house effect? (2002)
(a) infra-red rays
(b) ultra violet rays
(d) radio waves.
20. Biological importance of ozone layer is (2001)
(a) it stops ultraviolet rays
(b) ozone layer reduces green house effect
(c) ozone layer reflects radio waves
(d) ozone layer controls 02/H2 ratio in atmosphere.
21. The frequency order for y-rays (B), X-rays (A), UV rays (C) is (2000)
(a) B > A > C
(b) A > B > C
(c) C > B > A
(d) A > C > B.
22. Ozone layer blocks the radiations of wavelength (1999)
(a) more than 3 × 10-7 m
(b) equal to 3 × 10-7 m
(c) less than 3 × 10-7 m
(d) all of these
23. Wavelength of light of frequency 100 Hz (1999)
(a) 4 × 106 m
(b) 3 × 106 m
(c) 2 × 106 m ‘
(d) 5 × 10-5 m
24. If e0 and p0 are the electric permittivity and magnetic permeability in a free space, £ and p are the corresponding quantities in medium, the index and refraction of the medium is (1997)
25. Which of the following electromagnetic radiations have the smaller wavelength? (1994)
(c) UV waves
26. A signal emitted by an antenna from a certain point can be received at another point of the surface in the form of (1993)
(a) sky wave
(b) ground wave
(c) sea wave
(d) both (a) and (b)
27. The structure of solids is investigated by using (1992)
(a) cosmic rays
(d) infra-red radiations
28. The frequency of electromagnetic wave, which best suited to observe a particle of radius 3 × 104 cm is of the order of (1991)
29. In which of the following, emission of electrons does not take place (1990)
(a) thermionic emission
(b) X-rays emission
(c) photoelectric emission
(d) secondary emission
30. Which of the following electromagnetic radiations have the longest wavelength ? (1989)