Tiêu đề EECTROMAGNETICS WAVES (EMW).pdf ✅

Electromagnetic Waves  Digital www.allendigital.in [ 253 ] 1. If E and B are the electric and magnetic field vectors of electromagnetic waves then the direction of propagation of electromagnetic wave is along the direction of – (1) E (2) B (3) E × B (4) none of these 2. The electromagnetic waves do not transport - (1) energy (2) charge (3) momentum (4) information 3. The wave function (in S.I. units) for an electromagnetic wave is given as – 3 6 14  =   −  (x,t) 10 sin (3 10 x 9 10 t) The speed of the wave is – (1) 9 × 1014 m/s (2) 3 × 108 m/s (3) 3 × 106 m/s (4) 3 × 107 m/s 4. In the above problem, wavelength of the wave is – (1) 666 nm (2) 666 Å (3) 666 m (4) 6.66 nm 5. In an electromagnetic wave the average energy density is associated with – (1) electric field only (2) magnetic field only (3) equally with electric and magnetic fields (4) average energy density is zero 6. In an electromagnetic wave the energy density associated with magnetic field will be (1) 1 2 LI 2 (2) 2 0 B 2 (3) 2 0 1 B 2  (4) 0 2 1 2 B  7. In the above problem, the energy density associated with the electric field will be – (1) 1 2 CV 2 (2) 2 1q 2 C (3) 2 1 2 E  (4) 2 0 1 E 2  8. If there were no atmosphere, the average temperature on earth surface would be – (1) lower (2) higher (3) same (4) 0° C 9. In which part of earth's atmosphere is the ozone layer present? (1) troposphere (2) stratosphere (3) ionosphere (4) mesosphere 10. The ozone layer is earth's atmosphere is crucial for human survival because it – (1) contains ions (2) reflects radio signals (3) reflects ultraviolet rays (4) reflects infrared rays 11. The frequency from 3 × 109Hz to 3 × 1010Hz is – (1) high frequency band (2) super high frequency band (3) ultra high frequency band (4) very high frequency band 12. The frequency from 3MHz to 30 MHz is known as – (1) audio band (2) medium frequency band (3) very high frequency band (4) high frequency band 13. The AM range of radiowaves have frequency – (1) less than 30 MHz (2) more than 30 MHz (3) less than 20000Hz (4) more than 20000Hz 14. Select wrong statement from the following for EMW- (1) are transverse (2) travel with same speed in all medium (3) travel with the speed of light (4) are produced by accelerating charge 15. The waves related to tele-communication are - (1) infrared (2) visible light (3) microwaves (4) ultraviolet rays 16. The nature of electromagnetic wave is – (1) longitudinal (2) longitudinal stationary (3) transverse (4) transverse stationary Exercise - I
NEET : Physics [ 254 ] www.allendigital.in  Digital 17. Greenhouse effect keeps the earth surface – (1) cold at night (2) dusty and cold (3) warm at night (4) moist 18. The speed of electromagnetic radiation in vacuum is :- (1) 0 0 μ  (2)  0 0 (3) 0 0 1   (4) 0 0 1   19. What is the cause of greenhouse effect? (1) Infrared rays (2) Ultraviolet rays (3) X-rays (4) Radio waves 20. The conduction current is the same as displacement current when source is :- (1) ac only (2) dc only (3) both ac and dc (4) neither dc nor ac EXERCISE-I (Conceptual Questions) ANSWER KEY Question 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Answer 3 2 2 1 3 2 4 1 2 3 2 4 1 2 3 Question 16 17 18 19 20 Answer 3 3 4 1 3
Electromagnetic Waves  Digital www.allendigital.in [ 255 ] AIPMT 2009 1. The electric field part of an electromagnetic wave in a medium is represented by Ex = 0 ; Ey = 2.5 N C cos 6 2 rad rad 2 10 t 10 x s m −  −                    Ez = 0. The wave is : (1) Moving along –x direction with frequency 106 Hz and wavelength 200 m. (2) Moving along y direction with frequency 2 × 106 Hz and wavelength 200 m. (3) Moving along x direction with frequency 106 Hz and wavelength 100 m. (4) Moving along x direction with frequency 106 Hz and wavelength 200 m. AIPMT (Pre) 2010 2. Which of the following statement is false for the properties of electromagnetic waves? (1) These waves do not require any material medium for propagation (2) Both electric and magnetic field vectors attain the maxima and minima at the same place and same time (3) The energy in electromagnetic wave is divided equally between electric and magnetic vectors (4) Both electric and magnetic field vectors are parallel to each other and perpendicular to the direction of propagation of wave AIPMT (Pre) 2011 3. The dimensions of (μ00) –1/2 are : (1) [L1/2T–1/2] (2) [L–1T] (3) [LT–1] (4) [L–1/2T1/2] 4. The electric and the magnetic field, associated with an e.m. wave, propagating along the +z- axis, can be represented by :- (1) 0 0   E E i,B B j = = ˆ ˆ   (2) 0 0   E E k,B B i = = ˆ ˆ   (3) 0 0   E E j,B B i = = ˆ ˆ   (4) 0 0 ˆ ˆ   E E j,B B k = =   5. The decreasing order of wavelength of infrared, microwave, ultraviolet and gamma rays is : (1) microwave, infrared, ultraviolet, gamma rays (2) gamma rays, ultraviolet, infrared, microwaves (3) microwaves, gamma rays, infrared, ultraviolet (4) infrared, microwave, ultraviolet, gamma rays AIPMT (Pre) 2012 6. The electric field associated with an e.m. wave in vacuum is given by E = 40 cos (kz – 6 × 108t), where E, z and t are in volt/m, meterand seconds respectively. The value of wave vector k is : (1) 6m–1 (2) 3m–1 (3) 2m–1 (4) 0.5m–1 NEET-UG 2013 7. The condition under which a microwave oven heats up a food item containing water molecules most efficiently is :- (1) Infra-red waves produce heating in a microwave oven (2) The frequency of the microwaves must match the resonant frequency of the water molecules (3) The frequency of the microwaves has no relation with natural frequency of water molecules (4) Microwaves are heat waves, so always produce heating Re-AIPMT 2015 8. The energy of the em waves is of the order of 15 keV. To which part of the spectrum does it belong? (1) -rays (2) X-rays (3) Infra-red rays (4) Ultraviolet rays AIPMT 2015 9. A radiation of energy ‘E’ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (c = Speed of light) :- (1) 2E c (2) 2 2E c (3) 2 E c (4) E c Exercise - II (Previous Year Questions) AIPMT/NEET
NEET : Physics [ 256 ] www.allendigital.in  Digital NEET-I 2016 10. Out of the following options which one can be used to produce a propagating electromagnetic wave? (1) A charge moving at constant velocity (2) A stationary charge (3) A chargeless particle (4) An accelerating charge 11. A 100  resistance and a capacitor of 100  reactance are connected in series across a 220 V source. When the capacitor is 50% charged, the peak value of the displacement current is :- (1) 4.4 A (2) 11 2 A (3) 2.2 A (4) 11 A NEET (UG) 2017 12. In an electromagnetic wave in free space the root mean square value of the electric field is Erms = 6V/m. The peak value of the magnetic field is :- (1) 2.83 × 10–8 T (2) 0.70 × 10–8 T (3) 4.23 × 10–8 T (4) 1.41 × 10–8 T NEET (UG) 2018 13. An em wave is propagating in a medium with a velocity V Vi = ˆ . The instantaneous oscillating electric field of this em wave is along +y axis. Then the direction of oscillating magnetic field of the em wave will be along :- (1) –z direction (2) +z direction (3) –y direction (4) –x direction NEET (UG) 2019 (Odisha) 14. For a transparent medium relative permeability and permittivity, μr and r are 1.0 and 1.44 respectively. The velocity of light in this medium would be, (1) 2.5 × 108 m/s (2) 3 × 108 m/s (3) 2.08 × 108 m/s (4) 4.32 × 108 m/s NEET (UG) 2020 15. Light with an average flux of 20 W/cm2 falls on a non-reflecting surface at normal incidence having surface area 20 cm2. The energy received by the surface during time span of 1 minute is : (1) 48 × 103 J (2) 10 × 103 J (3) 12 × 103 J (4) 24 × 103 J 16. The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is : (c = speed of electromagnetic waves) (1) 1 : c2 (2) c : 1 (3) 1 : 1 (4) 1 : c NEET (UG) 2020 (COVID-19) 17. The E.M. wave with shortest wavelength among the following is (1) Ultraviolet rays (2) X-rays (3) Gamma-rays (4) Microwaves 18. The magnetic field in a plane electromagnetic wave is given by : By = 2 × 10–7 sin ( × 103 x + 3 × 1011t)T Calculate the wavelength. (1)  × 103 m (2) 2 × 10–3 m (3) 2 × 103 m (4)  × 10–3 m NEET (UG) 2021 19. A capacitor of capacitance 'C', is connected across an ac source of voltage V, given by V = V0sint. The displacement current between the plates of the capacitor, would then be given by : (1) Id = V0 C cost (2) 0 d C V I cos t  =  (3) 0 d V I sin t C =   (4) Id = V0 C sint 20. For a plane electromagnetic wave propagating in x-direction, which one of the following combinations gives the correct possible directions for electric field (E) and magnetic field (B) respectively? (1) ˆ ˆ ˆ ˆ j k, j k + + (2) ˆ ˆ ˆ ˆ − + − − j k, j k (3) ˆ ˆ ˆ ˆ j k, j k + − − (4) ˆ ˆ ˆ ˆ − + − + j k, j k