NCERT Exemplar Solutions

Physics

Q-13. An E.M. wave of intensity I falls on a surface kept in vacuum and exerts radiation pressure p on it. Which of the following are true?

(a) Radiation pressure is $\frac{\mathrm{I}}{\mathrm{C}}$ if the wave is totally absorbed.

(b) Radiation pressure is $\frac{\mathrm{I}}{\mathrm{C}}$ if the wave is totally reflected.

(c) Radiation pressure is $\frac{2\mathrm{I}}{\mathrm{C}}$ if the wave is totallyreflected.

(d) Radiation pressure is in the range $\frac{\mathrm{I}}{\mathrm{C}}<p<\frac{2\mathrm{I}}{\mathrm{C}}$ for real surfaces.

Physics

Q-12. The source of electromagnetic waves can be a charge

(a) moving with a constant velocity.

(b) moving in a circular orbit.

(c) at rest.

(d) falling in an electric field.

Physics

Q-11. A charged particle oscillates about its mean equilibrium position with a frequency of 109 Hz. The electromagnetic waves produced:

(a) will have frequency of 10⁹ Hz.

(b) will have frequency of 2 × 10⁹ Hz.

(c) will have a wavelength of 0.3 m.

(d) fall in the region of radiowaves

Physics

Q-10. A plane electromagnetic wave propagating along x direction can have the following pairs of E and B

(a) EX, BY.

(b) Ey, B.

(c) Bx, Ey.

(d) Ez, By

Physics

Q-9. An electromagnetic wave traveling along z-axis is given as:

 $\mathbf{E}\mathbf{=}{\mathbf{E}}_{\mathbf{\circ }}\mathbf{cos}\left(\mathrm{kz}-\mathrm{\omega t}\right)$. Choose the correct options from the following:

(a) The associated magnetic field is given as  $\mathrm{B}=\frac{1}{\mathrm{C}}\hat{\mathrm{k}}\times \mathrm{E}=\frac{1}{\mathrm{\omega }}\left(\hat{\mathrm{k}}\times \mathrm{E}\right)$             

(b) The electromagnetic field can be written in terms of the associated magnetic field as $\mathrm{E}=\mathrm{C}\left(\mathrm{B}\times \hat{\mathrm{k}}\right).$

(c) $\hat{\mathrm{k}}.\mathrm{E}=0, \hat{\mathrm{k}}.\mathrm{B}=0.$

(d) $\hat{\mathrm{k}}\times \mathrm{E}=0, \hat{\mathrm{k}}\times \mathrm{B}=0.$ 

Physics

Q-8. An electromognetic wave travels in vacuum along z direction: $\mathbf{E}\mathbf{=}\left(E_1\hat{i}+E_2 \hat{j}\right)\mathbf{ }\mathbf{cos}\left(\mathrm{kz}-\mathrm{\omega t}\right)$ . Choose the correct options from the following:

(a) The associated magnetic field is given as $\mathrm{B}=\frac{1}{C}({\mathrm{E}}_1\hat{\mathrm{i}}+{\mathrm{E}}_2 \hat{\mathrm{j}}) \cos (\mathrm{kz}-\mathrm{\omega t})$.

(b) The associated magnetic field is given as $\mathrm{B}=\frac{1}{C}({\mathrm{E}}_1\hat{\mathrm{i}}+{\mathrm{E}}_2 \hat{\mathrm{j}}) \cos (\mathrm{kz}-\mathrm{\omega t})$.

(c) The given electromagnetic field is circularly polarised.

(d) The given electromagnetic wave is plane polarised.