Properties of EM Waves - UNSOLVED PRACTICE SET
Chapter: Electromagnetic Waves | Topic: Properties of EM Waves
PROPERTIES OF EM WAVES - UNSOLVED PRACTICE SET
Topic: Properties of EM Waves
Multiple Choice Questions
Q1. Electromagnetic waves are:
- Longitudinal waves
- Transverse waves
- Mechanical waves
- Matter waves
Q2. In an electromagnetic wave, the electric field and magnetic field vectors are:
- Parallel to each other and parallel to the direction of propagation
- Parallel to each other and perpendicular to the direction of propagation
- Perpendicular to each other and perpendicular to the direction of propagation
- Perpendicular to each other with one parallel to the direction of propagation
Q3. The ratio of the amplitudes of electric field to magnetic field in an electromagnetic wave is equal to:
- The wavelength of the wave
- The frequency of the wave
- The speed of light in vacuum
- The energy of the photon
Q4. Electromagnetic waves carry:
- Only energy
- Only momentum
- Both energy and momentum
- Neither energy nor momentum
Q5. The energy density in an electromagnetic wave is:
- Only due to the electric field
- Only due to the magnetic field
- Equally shared between electric and magnetic fields
- Zero
Q6. The direction of propagation of an electromagnetic wave is given by:
- The direction of the electric field
- The direction of the magnetic field
- The direction of E × B
- The direction of B × E
Short Answer Questions
Q7. State four fundamental properties of electromagnetic waves.
Q8. Show that in an electromagnetic wave, the average energy density of the electric field equals the average energy density of the magnetic field.
Q9. What is the relationship between E₀ and B₀ in an electromagnetic wave? Write the expression and state what the ratio represents.
Q10. Do electromagnetic waves require a medium for propagation? Give evidence to support your answer.
Q11. Write the expression for the intensity of an electromagnetic wave in terms of E₀ and B₀.
Q12. What is radiation pressure? How does it demonstrate that electromagnetic waves carry momentum?
Long Answer Questions
Q13. Describe the transverse nature of electromagnetic waves. Explain with a diagram how the electric field, magnetic field, and direction of propagation are oriented relative to each other.
Q14. Derive the expression for the energy density of an electromagnetic wave. Show that the electric and magnetic energy densities are equal and find the total energy density.
Q15. Explain how electromagnetic waves carry momentum. Derive the expression for radiation pressure when the wave is completely absorbed and when it is perfectly reflected.
Numerical & Application-Based Problems
Q16. An electromagnetic wave in vacuum has an electric field amplitude E₀ = 100 V/m.
(a) Calculate the amplitude of the magnetic field B₀.
(b) Calculate the average energy density of the wave.
(c) Calculate the intensity of the wave.
(d) If this wave is completely absorbed by a surface of area 2 m² for 10 seconds, calculate the momentum transferred to the surface.
Q17. A laser beam with intensity 10⁸ W/m² is incident normally on a perfectly reflecting surface of area 1 cm².
(a) Calculate the radiation pressure exerted on the surface.
(b) Calculate the force exerted by the laser beam on the surface.
(c) If the same beam is incident on a perfectly absorbing surface, what would be the radiation pressure and force?
Q18. In your school's science fair, a student demonstrates the properties of electromagnetic waves using a simple setup with a radio transmitter.
(a) The student shows that when she rotates the receiving antenna, the signal strength changes. Explain which property of EM waves this demonstrates.
(b) She measures the electric field amplitude of a radio wave as 0.01 V/m at a distance of 1 km from the transmitter. Calculate the magnetic field amplitude at that point.
(c) The student places a metal sheet between the transmitter and receiver and the signal disappears. Explain why this happens and which property of EM waves is responsible.
(d) A classmate claims that sound waves and electromagnetic waves have the same properties because both are waves. Present three key differences between them to correct this misconception.