Frequently Asked Questions on Electromagnetic Waves
FAQs on Electromagnetic Waves Practice Paper for Students
1. What are electromagnetic waves?
Electromagnetic waves are transverse waves that consist of oscillating electric and magnetic fields perpendicular to each other and to the direction of wave propagation. Key properties include:
- Travel at the speed of light in vacuum (3 × 108 m/s)
- Do not require a medium to propagate
- Include forms like light, radio waves, X-rays and microwaves
2. What are the main characteristics of electromagnetic waves?
The main characteristics of electromagnetic waves are:
- Transverse nature: Electric and magnetic fields oscillate perpendicular to each other
- Travel at speed of light in vacuum
- Can propagate through vacuum (no medium required)
- Carry both energy and momentum
- Obey reflection, refraction, interference, and diffraction phenomena
3. What are the uses of electromagnetic waves?
Electromagnetic waves are widely used in daily life and technology, including:
- Radio waves for communication and broadcasting
- Microwaves in ovens and wireless networks
- Infrared radiation for remote controls and thermal imaging
- Visible light for vision and illumination
- X-rays for medical imaging
- Gamma rays for cancer treatment and sterilisation
4. What is the electromagnetic spectrum?
The electromagnetic spectrum is the complete range of electromagnetic waves, arranged according to their wavelength or frequency, including:
- Radio waves
- Microwaves
- Infrared radiation
- Visible light
- Ultraviolet rays
- X-rays
- Gamma rays
5. What is the speed of electromagnetic waves in vacuum?
All electromagnetic waves travel at the same speed in vacuum, which is 3 × 108 m/s (the speed of light).
6. Who discovered electromagnetic waves?
Heinrich Hertz was the first to experimentally generate and detect electromagnetic waves in 1887, confirming Maxwell's theory of electromagnetism.
7. What is meant by the transverse nature of electromagnetic waves?
Electromagnetic waves are called transverse because their electric and magnetic fields oscillate perpendicular to the direction of wave propagation, as well as to each other.
8. What is the relation between the electric and magnetic fields in an electromagnetic wave?
In an electromagnetic wave:
- The electric field (E) and magnetic field (B) are always perpendicular to each other
- The ratio of their magnitudes = speed of light (c), i.e., E/B = c
9. Write the Maxwell equations relevant to electromagnetic waves.
Maxwell's equations describe how electromagnetic waves are generated and propagate. The relevant equations are:
- ∇·E = ρ/ε₀
- ∇·B = 0
- ∇×E = -∂B/∂t
- ∇×B = μ₀ε₀ ∂E/∂t + μ₀J
10. Name the different types of electromagnetic waves in order of increasing frequency.
The types of electromagnetic waves in order of increasing frequency are:
- Radio waves
- Microwaves
- Infrared rays
- Visible light
- Ultraviolet rays
- X-rays
- Gamma rays
11. What is displacement current in the context of electromagnetic waves?
Displacement current is the current that arises due to a time-varying electric field in a dielectric, crucial for explaining electromagnetic wave propagation as described by Maxwell's equations.
12. How are electromagnetic waves produced?
Electromagnetic waves are produced by the acceleration or oscillation of electric charges, which generate changing electric and magnetic fields that propagate through space.






















