PYQSide ExamsMy practice

Electromagnetic Waves · Question 11

JEE Main 2026 (Online) 24th January Evening ShiftMCQEasy📈 Topic in 65% papers+4−1
1

A point source is kept at the center of a spherically enclosed detector. If the volume of the detector is increased by 8 times, the intensity will

  1. increase by 64 times
  2. decrease by 4 times
  3. decrease by 8 times
  4. increase by 8 times

Answer

(2) decrease by 4 times

Solution

V = 43 R3; V' = 8V R'3 = 8R3 R' = 2R

For a point source of power P: I = P4 R2 I 1R2

I'I = ( RR' )2 = 14

The intensity decreases by 4 times.

Answer: (2)

JEE Main 2026 (Online) 24th January Evening Shift

Keep practising — Electromagnetic Waves

2

Match List-I with List-II. Choose the correct answer from the options given below :

  1. A-I, B-IV, C-III, D-II
  2. A-II, B-III, C-IV, D-I
  3. A-IV, B-I, C-II, D-III
  4. A-II, B-III, C-I, D-IV
JEE Main 2026 (Online) 23rd January Morning Shift
3

The equation of the electric field of an electromagnetic wave propagating through free space is given by : E = 377 (6.27 103 t - 2.09 10-5 x) N/C The average intensity of the electromagnetic wave is ( 1 ) W/m2. The value of α is . (Take 0 0 = 377 in SI units )

JEE Main 2026 (Online) 23rd January Morning Shift
4

The ratio of speeds of electromagnetic waves in vacuum and a medium, having dielectric constant k = 3 and permeability of = 2 0, is ( 0 = permeability of vacuum)

  1. 6 : 1
  2. 3 : 2
  3. 6 : 1
  4. 36 : 1
JEE Main 2026 (Online) 23rd January Evening Shift
5

The electric field of a plane electromagnetic wave, travelling in an unknown nonmagnetic medium is given by, Ey = 20 (3 106 x - 4.5 1014 t ) V/m (where x, t and other values have S.I. units). The dielectric constant of the medium is (speed of light in free space is 3 108 m/s)

JEE Main 2026 (Online) 22nd January Morning Shift
6

A laser beam has intensity of 4.0 1014 W/m2. The amplitude of magnetic field associated with beam is T. (Take 0 = 8.85 10-12 C2/Nm2 and c = 3 108 m/s)

  1. 1.83
  2. 2.0
  3. 5.5
  4. 18.3
JEE Main 2026 (Online) 22nd January Evening Shift
7

If , E and t represent the free space permittivity, electric field and time respectively, then the unit of Et will be :

  1. Am
  2. A/m
  3. A/m2
  4. Am2
JEE Main 2026 (Online) 22nd January Evening Shift
8

The electric field in a plane electromagnetic wave is given by : Ey = 69 [0.6 103x - 1.8 1011t ] V/m. The expression for magnetic field associated with this electromagnetic wave is T.

  1. Bz = 2.3 10-7 [0.6 103x - 1.8 1011t ]
  2. Bz = 2.3 10-7 [0.6 103x + 1.8 1011t ]
  3. By = 2.3 10-7 [0.6 103x - 1.8 1011t ]
  4. By = 69 [0.6 103x + 1.8 1011t ]
JEE Main 2026 (Online) 21st January Morning Shift
9

An electromagnetic wave of frequency 100 MHz propagates through a medium of conductivity, = 10 mho/m. The ratio of maximum conduction current density to maximum displacement current density is . [Take 14 0 = 9 109 N m2/C2]

JEE Main 2026 (Online) 21st January Evening Shift
10

If 0 denotes the permittivity of free space and E is the flux of the electric field through the area bounded by the closed surface, then dimensions of ( 0 d Edt ) are that of :

  1. electric charge
  2. electric field
  3. electric current
  4. electric potential
JEE Main 2025 (Online) 7th April Morning Shift
11

The unit of 2I 0 c is : (I = intensity of an electromagnetic wave, c = speed of light)

  1. Vm
  2. NC-1
  3. NC
  4. Nm
JEE Main 2025 (Online) 7th April Evening Shift

All Electromagnetic Waves PYQs →

PDFDownload Electromagnetic Waves PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All JEE Main Physics chapters