Which of the following are properties of electromagnetic waves?
I. They can be propagated through space without a medium.
II. They carry energy proportional to their frequency.
III. They are all harmful to humans.
a. I only
b. II only
c. I and II only
d. I, II, and III only
The Correct answer and Explanation is:
The correct answer is c. I and II only.
Explanation:
Electromagnetic waves possess several fundamental properties that characterize their behavior and interactions with matter. Let’s break down the statements provided in the question:
I. They can be propagated through space without a medium.
This statement is true. Unlike sound waves, which require a material medium (such as air, water, or solids) to travel, electromagnetic waves can propagate through a vacuum. This is a unique characteristic of electromagnetic radiation and allows for the transmission of light from the Sun to Earth through the vastness of space.
II. They carry energy proportional to their frequency.
This statement is also true. The energy EEE carried by an electromagnetic wave is directly proportional to its frequency fff, as described by the equation E=hfE = hfE=hf, where hhh is Planck’s constant (approximately 6.626×10−346.626 \times 10^{-34}6.626×10−34 Joule-seconds). This means that higher frequency electromagnetic waves, such as gamma rays and X-rays, carry more energy compared to lower frequency waves like radio waves.
III. They are all harmful to humans.
This statement is false. While some electromagnetic waves, particularly those in the higher frequency range (such as ultraviolet rays, X-rays, and gamma rays), can indeed be harmful and can cause damage to biological tissues (including increasing the risk of cancer), not all electromagnetic waves are harmful. For instance, visible light is necessary for life, and radio waves are generally harmless. In fact, many forms of electromagnetic radiation, like microwaves, are safely used in everyday appliances.
In summary, statements I and II are correct regarding the properties of electromagnetic waves, while statement III is misleading. Thus, the properties of electromagnetic waves that are accurate are encapsulated in option c: I and II only.