An object is placed in a medium of refractive index 3. An electromagnetic wave of intensity $6 \times 10^{8} \mathrm{~W} / \mathrm{m}^{2}$ falls normally on the object and it is absorbed completely. The radiation pressure on the object would be (speed of light in free space $=3 \times 10^{8} \mathrm{~m} / \mathrm{s}$) :

JEE Main · 2024 · 27 Jan 2024 · Shift 2 · EM Waves

An object is placed in a medium of refractive index 3. An electromagnetic wave of intensity

6 \times 1 0^{8} W / m^{2}

falls normally on the object and it is absorbed completely. The radiation pressure on the object would be (speed of light in free space

= 3 \times 1 0^{8} m / s

) :

(A) $36 Nm^{- 2}$
(B) $18 Nm^{- 2}$
(C) $6 Nm^{- 2}$ ✓ Correct
(D) $2 Nm^{- 2}$

Answer: (C)

Solution

For a wave completely absorbed inside a medium of refractive index

μ

, the radiation pressure is

P = I / v

, where

v = c / μ

is the speed of light in that medium, so

P = \frac{I μ}{c} = \frac{( 6 \times 1 0 ^{8} ) ( 3 )}{3 \times 1 0 ^{8}} = 6 N/m^{2} .

JEE Main · 2024 · 27 Jan 2024 · Shift 2 · Single correct option

Practise more: all JEE Main PYQs on EM Waves →

More JEE Main questions on EM Waves

The electric field of a plane electromagnetic wave, travelling in an unknown non-magnetic medium is given by,
$E_{y} = 20 sin (3 \times 1 0^{6} x - 4.5 \times 1 0^{14} t) V / m$
(where $x, t$ and ot …
JEE Main 2026View solution →
A laser beam has intensity of $4.0 \times 1 0^{14} W / m^{2}$ . The amplitude of magnetic field associated with beam is ______ T. (Take $ϵ_{0} = 8.85 \times 1 0^{- 12} C^{2} / Nm^{2}$ and $c = 3 \times 1 0^{8} m / s$ )
JEE Main 2026View solution →
An electromagnetic wave of frequency 100 MHz propagates through a medium of conductivity, $σ = 10 mho / m$ . The ratio of maximum conducting current density to maximum displacement current density is ____ .

$[$ Take …
JEE Main 2026View solution →
The equation of the electric field of an electromagnetic wave propagating through free space is given by :
$E = 377 sin (6.27 \times 1 0^{3} t - 2.09 \times 1 0^{- 5} x)$ N/C
The average power of the electromagnetic wave is $(\frac{1}{α})$ W/m $^{2}$ . T …
JEE Main 2026View solution →
The ratio of speeds of electromagnetic waves in vacuum and a medium, having dielectric constant $k = 3$ and permeability of $μ = 2 μ_{0}$ , is ( $μ_{0} =$ permeability of vacuum)
JEE Main 2026View solution →
The electric field of an electromagnetic wave travelling through a medium is given by
$E (x, t) = 25 sin (2.0 \times 1 0^{15} t - 1 0^{7} x) \overset{n}{^}$
then the refractive index of the medium is ______.
(All given measurement are in SI units)
JEE Main 2026View solution →