Question

When an electromagnetic wave encounters a dielectric medium, the transmitted wave has (A) same frequency but different amplitude (B) same amplitude but different frequency (C) same frequency and amplitude (D) different frequency and amplitude

Short answer

Based on the analysis, when an electromagnetic wave encounters a dielectric medium, the transmitted wave has the same frequency but different amplitude. This is because the frequency is a property of the source and remains unchanged during transmission, while the amplitude may get reduced due to partial reflection or absorption of the wave in the medium. Therefore, the correct answer is (A) same frequency but different amplitude.

Step-by-step solution

Recall characteristics of electromagnetic waves

When an electromagnetic wave interacts with a dielectric medium, some part of the wave is reflected, and the remaining is transmitted through the medium. The speed of the transmitted wave changes due to the dielectric properties of the medium. The wave's electric field interacts with the medium's particles, causing the wave's speed to change. However, the frequency of the wave remains constant across the interface.

Compare given options with wave properties in a dielectric medium

Now we will analyze each of the given options and compare them with the properties of the transmitted wave in a dielectric medium. (A) same frequency but different amplitude - The transmitted wave has the same frequency as the incident wave because frequency is a property of the source and remains unchanged during transmission. The amplitude may get reduced due to partial reflection or absorption of the wave in the medium. (B) same amplitude but different frequency - As discussed earlier, the frequency remains constant, and the amplitude may change. So, this option is incorrect. (C) same frequency and amplitude - The frequency is the same, but the amplitude may change due to absorption or reflection within the medium. Hence, this option is not correct. (D) different frequency and amplitude - We have established that the frequency remains constant, so this option is incorrect.

Conclusion

Based on the above analysis, we can determine that the correct answer is: (A) same frequency but different amplitude

Key concepts

Dielectric Medium

A dielectric medium is a type of insulating material that does not conduct electricity. When electromagnetic waves pass through such a medium, it influences the wave's speed but does not allow electric current to flow.

The interaction between the waves and the dielectric medium occurs because the medium's molecules become polarized. This means that the molecules align their electric charges in response to the passing wave's electric field.

This interaction leads to changes in some aspects of the wave's travel, but notably, it does not affect its frequency. Instead, it primarily influences the wave's speed and sometimes its amplitude.

Amplitude Change

Amplitude refers to the height or intensity of the wave. When an electromagnetic wave encounters a dielectric medium, the amplitude can undergo a change.

Typically, the amplitude may decrease due to two primary reasons:

• Reflection: Part of the wave's energy is reflected back at the boundary of the medium.
• Absorption: The medium itself absorbs some of the wave's energy, slightly reducing its intensity.

Despite these alterations in amplitude, the wave's frequency remains unaffected. This change in amplitude is crucial as it affects how the wave propagates and interacts with the medium.

Frequency Constancy

The frequency of a wave is determined by the source of the wave and remains constant regardless of the medium through which it travels. This is why, even when electromagnetic waves enter a dielectric medium, their frequency stays the same.

The unchanged frequency is a significant property because it does not depend on the medium's properties, unlike amplitude and speed.

This consistency is fundamental for applications like telecommunications, where information is encoded at specific frequencies.

Wave Transmission Through Media

When electromagnetic waves travel from one medium to another, they undergo changes, but some aspects remain constant. This is referred to as wave transmission through media.

The wave transmission process involves:

• Reflection: Part of the wave reflects back into the original medium.
• Refraction: The wave bends as it enters the new medium, changing speed.
• Transmission: The wave continues through the new medium with possibly altered amplitude.

While the amplitude and speed of the wave may change, the frequency stays constant, ensuring that the information carried by the wave remains unchanged. Understanding these principles is vital for designing systems that use electromagnetic waves, such as communication networks and medical imaging devices.