Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app

JEE Main 202623 JanuaryEvening Shift

Exam: JEE Main
Year: 2026
Date: 23 January
Shift: Evening Shift
Subject: Physics
Chapter: Electromagnetic Waves

JEE Main 2026 · 23 January · Evening Shift · Physics · Electromagnetic Waves

The ratio of speeds of electromagnetic waves in vacuum and a...

The ratio of speeds of electromagnetic waves in vacuum and a medium, having dielectric constant

k=3

and permeability of

\mu=2 \mu_{0}

, is
(

\mu_{0}=

permeability of vacuum)

Options

A $36: 1$
B $3: 2$
C $6: 1$
D $\sqrt{6}: 1$

Correct answer

D. $\sqrt{6}: 1$

Step-by-step solution

Speed of electromagnetic wave in vacuum:

c = \frac{1}{\sqrt{\mu_0 \epsilon_0}}

Speed in a medium with permeability

\mu = 2\mu_0

and dielectric constant

k = 3

:

v = \frac{1}{\sqrt{\mu \epsilon}} = \frac{1}{\sqrt{2\mu_0 \times 3\epsilon_0}} = \frac{1}{\sqrt{6\mu_0\epsilon_0}}

v = \frac{1}{\sqrt{6}} \times \frac{1}{\sqrt{\mu_0\epsilon_0}} = \frac{c}{\sqrt{6}}

Ratio of speeds:

\frac{c}{v} = \sqrt{6}

Therefore:

c : v = \sqrt{6} : 1

Practice Electromagnetic Waves on Quantrex Academy →

More from Electromagnetic Waves

The electric field associated with an electromagnetic wave travelling in vacuum is given… JEE Advanced 2026 A monochromatic source of light operating at 15 kW emits 2.5× 10^ 22 photons/s. The… JEE Main 2026 For an electromagnetic wave propagating through vacuum, k , E and ω represent propagation… JEE Main 2026 A point light source emits E.M. waves in free space. A detector, placed at a distance of… JEE Main 2026 A displacement current of 4.0 A can be set up in the space between two parallel plates of… JEE Main 2026 A magnetic field vector in an electromagnetic wave is represented by B =B_0 (2π vt-(2π… JEE Main 2026 An electromagnetic wave travels in free space along the x -direction. At a particular… JEE Main 2026 An electromagnetic wave travelling in x -direction is described by field equation E_y =… JEE Main 2026 Full Electromagnetic Waves list All JEE Main PYQs