1. Which of the following represents the speed of electromagnetic waves in a vacuum?
Answer:
Explanation:
Electromagnetic waves travel at the speed of light in a vacuum, which is approximately 3 x 10^8 m/s.
2. Which of the following is NOT an electromagnetic wave?
Answer:
Explanation:
Sound waves are mechanical waves and require a medium to propagate, unlike electromagnetic waves.
3. Which electromagnetic waves have the shortest wavelength?
Answer:
Explanation:
Gamma rays have the shortest wavelength in the electromagnetic spectrum.
4. Electromagnetic waves are transverse in nature because:
Answer:
Explanation:
One of the properties of transverse waves is polarization, which is exhibited by electromagnetic waves.
5. Which part of the electromagnetic spectrum is primarily used for communication?
Answer:
Explanation:
Radio waves are extensively used for various communication purposes including broadcasting.
6. The electromagnetic waves that help in the study of the molecular structure of crystals are:
Answer:
Explanation:
X-rays are used in X-ray crystallography to study the molecular structure of crystals.
7. Which of the following can be blocked by the Earth's ozone layer?
Answer:
Explanation:
The ozone layer absorbs most of the harmful ultraviolet (UV) rays from the sun.
8. The electric and magnetic fields in an electromagnetic wave are:
Answer:
Explanation:
In an electromagnetic wave, the electric and magnetic fields are perpendicular to each other and also to the direction of wave propagation.
9. Infrared waves are primarily used for:
Answer:
Explanation:
Infrared waves are employed in night vision devices as they detect heat.
10. Which of the following has the highest frequency?
Answer:
Explanation:
Gamma rays have the highest frequency in the electromagnetic spectrum.
11. Which of the following waves is NOT harmful to the human body?
Answer:
Explanation:
Radio waves are non-ionizing and are generally considered safe for the human body.
12. Which of the following best describes the phenomenon of the generation of an EM wave?
Answer:
Explanation:
Electromagnetic waves are generated by accelerated charges.
13. The phenomenon by which an unpolarized light gets polarized when passed through certain materials is known as:
Answer:
Explanation:
The process in which unpolarized light becomes polarized due to scattering is known as polarization by scattering.
14. In the electromagnetic spectrum, the waves used for satellite communication are:
Answer:
Explanation:
Microwaves, due to their desirable properties, are used in satellite communication.
15. Electromagnetic waves can travel in a vacuum because:
Answer:
Explanation:
Electromagnetic waves are non-mechanical and can propagate without a medium.
16. The human eye is most sensitive to which part of the electromagnetic spectrum?
Answer:
Explanation:
The human eye is sensitive to visible light, which is why we can see it.
17. Which of the following waves can penetrate through opaque objects?
Answer:
Explanation:
X-rays can penetrate through many opaque materials, which is why they're used in medical imaging.
18. The primary source of electromagnetic waves is:
Answer:
Explanation:
Electromagnetic waves are produced by accelerated charges.
19. Which of the following is responsible for the green house effect?
Answer:
Explanation:
Infrared radiation is responsible for the green house effect, as it gets trapped within the Earth's atmosphere.
20. Which wave can be produced by the thermal motion of atoms and molecules?
Answer:
Explanation:
Infrared rays are produced by the thermal motion of atoms and molecules.