JEE Main · 2025 · 03 Apr 2025 · Shift 1 · EM Waves

WhatsApp Email

The radiation pressure exerted by a 450 W light source on a perfectly reflecting surface placed at 2 m away from it, is :

(A) $1.5 \times 1 0^{- 8}$ Pascals
(B)0
(C) $6 \times 1 0^{- 8}$ Pascals✓ Correct
(D) $3 \times 1 0^{- 8}$ Pascals

Answer: (C)

Solution

The surface reflects perfectly, so the radiation pressure is

P = \frac{2 I}{c}

, where

I

is the intensity reaching it. Treating the lamp as a point source, the intensity at

r = 2 m

I = \frac{P _{src}}{4 π r ^{2}} = \frac{450}{4 π \times 4} = \frac{450}{16 π} W/m^{2} .

Therefore

P = \frac{2}{c} \cdot \frac{450}{16 π} = \frac{900}{16 π \times 3 \times 1 0 ^{8}} \approx 6 \times 1 0^{- 8} Pa .

The radiation pressure is about

6 \times 1 0^{- 8}

Pascals.

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · 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 →