Problem 2203 - JEE Physics

Question

Which of the following waves are not transverse in nature? (A) light emitted from a sodium lamp (B) sound waves travelling in air (C) \(\mathrm{x}\) rays from an \(\mathrm{x}\) ray machine (D) microwaves used in radar

Step-by-Step Solution

Answer

The only wave that is not transverse in nature among the given options is (B) sound waves traveling in air, as it is a longitudinal wave.

Step 1: Determine the wave types for each option

To determine if a wave is transverse or not, we need to understand the nature of each wave. (A) Light emitted from a sodium lamp - This type of wave is an electromagnetic wave. Electromagnetic waves are transverse in nature, as their electric and magnetic fields oscillate perpendicular to the direction of energy propagation. (B) Sound waves traveling in air - Sound waves are mechanical waves that travel through a medium such as air. In a sound wave, the particles in the medium oscillate parallel to the direction of the wave's energy propagation, making it a longitudinal wave. (C) X-rays from an X-ray machine - X-rays, like light waves emitted from a sodium lamp, are also electromagnetic waves. Hence, they are transverse in nature. (D) Microwaves used in radar - Microwaves are a type of electromagnetic wave, just like light waves and X-rays. Therefore, they are also transverse in nature.

Step 2: Identify the wave that is not transverse

From our analysis in Step 1, we know the wave types for each option: (A) Light emitted from a sodium lamp - Transverse (B) Sound waves traveling in air - Longitudinal (C) X-rays from an X-ray machine - Transverse (D) Microwaves used in radar - Transverse The question asks which wave is not transverse in nature. The only wave that is not a transverse wave is the sound wave traveling in air (Option B). Therefore, the correct answer is (B) sound waves traveling in air.

Key Concepts

Electromagnetic Waves

Electromagnetic waves are fascinating phenomena that play a crucial role in our daily lives. They are transverse waves, meaning their oscillations occur perpendicular to the direction of wave travel. Unlike mechanical waves, electromagnetic waves do not require a medium to propagate. This means they can travel through the vacuum of space.
For example:

• Light emitted from a sodium lamp is an electromagnetic wave, which is why it is transverse.
• X-rays from a machine are another example of electromagnetic waves, used widely in medical imaging due to their ability to penetrate various materials.
• Microwaves, employed in radar technology and household appliances, are also transverse electromagnetic waves.

The properties of these waves, such as their speed (approximately 3 x 10^8 m/s in a vacuum), are consistent across different types of electromagnetic waves. These waves also exhibit behaviors such as reflection, refraction, and diffraction, making them indispensable in technology and science.

Mechanical Waves

Mechanical waves are waves that require a medium to travel through. The particles within this medium oscillate to transfer energy from one point to another. Mechanical waves can be further classified into transverse and longitudinal waves.
Sound waves, for instance, are mechanical and longitudinal. The particles in the air (the medium) vibrate parallel to the direction of the wave's energy travel. This is why sound waves cannot travel through a vacuum—they need a medium, like air or water.
In general, mechanical waves:

• Need a material medium (solid, liquid, or gas) to move through.
• Can be either transverse (like water waves) or longitudinal (like sound waves).
• Exhibit properties such as wavelength, frequency, and amplitude.

Understanding mechanical waves helps explain everyday phenomena, such as why we can hear sounds or see waves in the ocean.

Wave Propagation

Wave propagation is the transmission of energy through a medium via waves. It differs between electromagnetic and mechanical waves due to their underlying nature.

For electromagnetic waves, propagation involves the oscillation of electric and magnetic fields through space without needing a medium. They can travel vast distances through a vacuum, which is why we are able to communicate with satellites.

Mechanical waves, meanwhile, rely on particle interaction within a medium. For example, a sound wave propagates through air by creating compressions and rarefactions of particles, transmitting sound from one point to another.

Key things to remember about wave propagation:

• Electromagnetic waves don't need a medium, traveling at the speed of light in a vacuum.
• Mechanical waves rely on a medium, transferring energy through particle motion.
• The medium's properties can affect wave speed and behavior.

Recognizing how waves propagate helps us understand different technologies, from radio signals to sonic booms.