An EM wave of intensity I falls on a surface kept in vacuum and exerts radiation pressure p on it. Which of the following are true? Radiation pressure is Ic if the wave is totally absorbed - Physics

Advertisements
Advertisements
MCQ

An EM wave of intensity I falls on a surface kept in vacuum and exerts radiation pressure p on it. Which of the following are true?

  1. Radiation pressure is `I/c` if the wave is totally absorbed.
  2. Radiation pressure is `I/c` if the wave is totally reflected.
  3. Radiation pressure is `(2I)/c` if the wave is totally reflected.
  4. Radiation pressure is in the range `I/c < p < (2I)/c` for real surfaces.

Options

  • a, b and c

  • b, c and d

  • a, c and d

  • c and d

Advertisements

Solution

a, c and d

Explanation:

Radiation pressure (p) is the force exerted by electromagnetic waves on unit area of the surface, i.e., rate of change of momentum per unit area of the surface.

Let us consider a surface exposed to electromagnetic radiation as shown in figure. The radiation is falling normally on the surface. Further, intensity of radiation is I and area of surface exposed to radiation is A.

Radiation pressure is the force exerted by particles (dual nature of particle) on unit area, due to the charge in momentum of radiated particles per unit area per sec = `I/c`.

I = Intensity pf radiation

C = Velocity of radiation

Radiations are absorbed, so momentum per unit area second = `I/c`.

When radiation is reflected back, the momentum becomes double as in earlier case.

So variation of radiation pressure p comes between the range `I/c < p < (2I)/c`.

  Is there an error in this question or solution?
Chapter 8: Electromagnetic Waves - MCQ I [Page 50]

APPEARS IN

NCERT Exemplar Physics Class 12
Chapter 8 Electromagnetic Waves
MCQ I | Q 8.13 | Page 50

Video TutorialsVIEW ALL [2]

RELATED QUESTIONS

How are em waves produced by oscillating charges?


Suppose that the electric field amplitude of an electromagnetic wave is E0 = 120 N/C and that its frequency is v = 50.0 MHz.

(a) Determine, B0, ω, k, and λ.

(b) Find expressions for E and B.


Do electromagnetic waves carry energy and momentum ?


Identify the electromagnetic waves whose wavelengths vary as:

(a) 10–12 m < λ < 10–8 m

(b) 10–3 m < λ < 10–1 m

Write one use for each.


What is the ratio of the speed of gamma rays to that of radio waves in a vacuum?


How are electric vector `(vec "E")`, magnetic vector `(vec "B")` and velocity vector `(vec "C")` oriented in an electromagnetic wave?


Which em waves lie near the high frequency end of visible part of em spectrum? Give its one use. In what way this component of light has harmful effects on humans?


Write the following radiations in ascending order with respect to their frequencies:

X-rays, microwaves, UV rays and radio waves.


How does a charge q oscillating at certain frequency produce electromagnetic waves?

Sketch a schematic diagram depicting electric and magnetic fields for an electromagnetic wave propagating along the Z-direction.


Can an electromagnetic wave be deflected by an electric field or a magnetic field?


A wire carries an alternating current i = i0 sin ωt. Is there an electric field in the vicinity of the wire?


A plane electromagnetic wave is passing through a region. Consider (a) electric field (b) magnetic field (c) electrical energy in a small volume and (d) magnetic energy in a small volume. Construct the pairs of the quantities that oscillate with equal frequencies.


An electromagnetic wave going through vacuum is described by
E = E0 sin (kx − ωt); B = B0 sin (kx − ωt).
Which of the following equations is true?


Displacement current goes through the gap between the plates of a capacitor when the charge of the capacitor

(a) increases
(b) decreases
(c) does not change
(d) is zero


Speed of electromagnetic waves is the same


The energy contained in a small volume through which an electromagnetic wave is passing oscillates with


Consider the situation of the previous problem. Define displacement resistance Rd = V/idof the space between the plates, where V is the potential difference between the plates and id is the displacement current. Show that Rd varies with time as `R_d = R(e^(t"/"tau) - 1)` .


A laser beam has intensity 2.5 × 1014 W m−2. Find amplitudes of electric and magnetic fields in the beam.


The energy associated with light of which of the following colours is minimum : 


This is an example of step-up transformer .


Define frequency modulation and state any one advantage of frequency modulation (FM) over amplitude modulation (AM). 


State any one property which is common to all electromagnetic waves.


The energy levels of an atom of a certain element are shown in the given figure. Which one of the transitions A, B, C, D or E will result in the emission of photons of electromagnetic radiation of wavelength 618.75 nm? Support your answer with mathematical calculations.


The dimension of `1/(mu_0 ∈_0)` is


Which of the following electromagnetic radiations is used for viewing objects through fog ______.


Consider an oscillator which has a charged particle oscillating about its mean position with a frequency of 300 MHz. The wavelength of electromagnetic waves produced by this oscillator is ______.


The electric and magnetic fields, associated with an electromagnetic wave, propagating along negative X-axis can be represented by ______.


In an electromagnetic wave in free space the rms value of the electric field is 3 V m-1. The peak value of the magnetic field is ______.


Which of the following is NOT true for electromagnetic waves?


Give two uses of IR radiation.


Write down Maxwell equations in integral form.


Write a short note on the visible spectrum.


Explain the Maxwell’s modification of Ampere’s circuital law.


Wavelength λ and wave vector k are related by ______.


The speed of plane electromagnetic waves is maximum in ______.


Which one of the following does not represent simple harmonic motion? Here y denotes the instantaneous displacement. Here, A and B are constants and co is the angular frequency.


A plane electromagnetic wave travels in free space along x-axis. At a particular point in space, the electric field along y-axis is 9.3 Vm−1. The magnetic induction (B) along z-axis is:


Dimensions of 1/(µOE0) is


An accelerate electron would produce.


Maxwell's equation describe the fundamental law of


If a source is transmitting electromagnetic waves of frequency 8.2 × 106 Hz. then wavelength of electromagnetic waves transmitted from the source will be.


The velocity of light in vacuum can be changed by changing


Which of the following are not electromagnetic waves?


Dimensions of ε0 `(d phi_ε)/(dt)` are of


Electromagnetic waves are produced by ______.


Which of the following type of radiations are radiated by an oscillating electric charge?


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?


For a plane electromagnetic wave propagating in the x-direction, which one of the following combinations gives the correct possible directions for the electric field (E) and magnetic field (B) respectively?


Show that the radiation pressure exerted by an EM wave of intensity I on a surface kept in vacuum is I/c.


A plane EM wave travelling in vacuum along z direction is given by `E = E_0 sin(kz - ωt)hati` and `B = B_0 sin(kz - ωt)hatj` 

  1. Evaluate `oint E.dl` over the rectangular loop 1234 shown in figure.
  2. Evaluate `int B.ds` over the surface bounded by loop 1234.
  3. Use equation `oint E.dl = (-dphi_B)/(dt)` to prove `E_0/B_0` = c.
  4. By using similar process and the equation `ointB.dl = mu_0I + ε_0 (dphi_E)/(dt)`, prove that c = `1/sqrt(mu_0ε_0)`


The intensity of the light from a bulb incident on a surface is 0.22 W/m2 . The amplitude of the magnetic field in this light-wave is ______× 10–9 T. 

(Given: Permittivity of vacuum ε0 = 8.85 × 10–12 C2 N–1 – m–2, speed of light in vacuum c = 3 × 108 ms-1)


A plane electromagnetic wave of frequency 500 MHz is travelling in a vacuum along a y-direction.

At a particular point in space and time, `vec"B"` = 8.0 × 10-8 `hat"Z"`T. The value of the electric field at this point is ______.

(speed of light = 3 × 108 ms-1)

`hat x, hat y, hat z` are unit vectors along x, y, and Z directions.


For an electromagnetic wave travelling in free space, the relation between average energy densities due to electric (Ue) and magnetic (Um) fields is ______.


Sunlight falls normally on a surface of area 36 cm2 and exerts an average force of 7.2 × 10-9 N within a time period of 20 minutes. Considering a case of complete absorption the energy flux of incident light is ______.


The electric field in an electromagnetic wave is given by E = 56.5 sin ω(t - x/c)Nc-1. Find the intensity of the wave if it is propagating along x-axis in the free space.

(Given ε0 = 8.85 × 10-12 C2 N-1 m-2)


A plane electromagnetic wave with frequency of 30 MHz travels in free space. At particular point in space and time, electric field is 6 V/m. The magnetic field at this point will be x × 10-8 T. The value of x is ______.


An electromagnetic wave of frequency 3 GHz enters a dielectric medium of relative electric permittivity 2.25 from vacuum. The wavelength of this wave in that medium will be ______ × 10-2 cm. 


In a plane electromagnetic wave, the direction of electric field and magnetic field are represented by `hat"k"` and 2`hat"i" - 2hat"j"`, respectively. What is the unit vector along direction of propagation of the wave.


A 27 mW laser beam has a cross-sectional area of 10 mm2. The magnitude of the maximum electric field in this electromagnetic wave is given by:

[Given permittivity of space ∈0 = 9 × 10-12 SI units, Speed of light c = 3  108 m/s] 


An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with permittivity ∈ = 4.0. Then ______.


Name the electromagnetic wave/radiation which is used to study crystal structure.


Share
Notifications



      Forgot password?
Use app×