Consider the two statements given below : Statement-1: Infrared waves are also called heat waves. Statement-2: Water molecules readily absorb infrared waves. Select the correct answer using the code given below:
Understanding Infrared Waves and Heat
The question asks us to evaluate two statements about infrared waves and their relationship to heat and water absorption.
Analyzing Statement-1: Infrared waves are also called heat waves.
Statement-1 claims that infrared waves are known as heat waves. Let's consider what infrared waves are. They are a part of the electromagnetic spectrum with wavelengths longer than visible light and shorter than microwaves. When objects absorb electromagnetic radiation, their internal energy increases, which we perceive as heat. Infrared radiation is particularly efficient at transferring heat between objects through radiation. Objects at typical Earth temperatures (like the human body, furniture, the ground) emit radiation primarily in the infrared range. When this radiation is absorbed by another object, it causes that object to heat up. This strong association with heat transfer via radiation is why infrared waves are commonly referred to as heat waves or radiant heat.
Therefore, Statement-1 is true.
Analyzing Statement-2: Water molecules readily absorb infrared waves.
Statement-2 states that water molecules easily absorb infrared waves. Molecules have different modes of vibration and rotation, and these modes correspond to specific energy levels. Transitions between these energy levels can occur when the molecule absorbs photons with the corresponding energy (and frequency/wavelength). Water molecules (H₂O) have several vibrational and rotational modes that strongly absorb radiation in the infrared part of the electromagnetic spectrum. This strong absorption of infrared radiation by water is significant in many phenomena, including the heating of water by radiation and the greenhouse effect in Earth's atmosphere (as water vapor is a major greenhouse gas). Experiments and theoretical studies confirm that water is a strong absorber of infrared radiation.
Therefore, Statement-2 is true.
Evaluating the Relationship Between Statements
Now we need to consider if Statement-2 is a correct explanation for Statement-1. Statement-1 says infrared waves are called heat waves because they transfer heat. Statement-2 says water molecules readily absorb infrared waves. If water molecules (which are abundant in the environment, living organisms, and the atmosphere) strongly absorb infrared waves, this absorption leads to an increase in their kinetic energy, which is experienced as heat. The fact that many common substances, including water, efficiently absorb infrared radiation means that when this radiation falls on them, it causes them to heat up. This strong heating effect upon absorption is precisely why infrared waves are called heat waves. The ready absorption of infrared by substances like water is a key mechanism by which infrared radiation transfers heat, thus explaining why it gets its common name.
Therefore, Statement-2 provides a correct explanation for why Statement-1 is true.
Based on the analysis:
- Statement-1 is true.
- Statement-2 is true.
- Statement-2 explains Statement-1.
| Statement | Validity | Explanation |
|---|---|---|
| Statement-1: Infrared waves are also called heat waves. | True | Infrared radiation is effective at transferring heat via radiation. |
| Statement-2: Water molecules readily absorb infrared waves. | True | Water molecules have vibrational modes that match infrared frequencies, leading to strong absorption. |
Conclusion: Both statements are individually true, and Statement-2 is the correct explanation of Statement-1.
Revision Table: Key Concepts of Infrared Waves
| Concept | Description |
|---|---|
| Infrared Waves | Electromagnetic radiation with wavelengths longer than visible light and shorter than microwaves. |
| Heat Waves | Common term for infrared waves due to their strong association with heat transfer via radiation. |
| Absorption by Water | Water molecules efficiently absorb infrared radiation, leading to increased thermal energy. |
| Mechanism of Absorption | Absorption occurs when infrared photons excite the vibrational and rotational modes of molecules like water. |
Additional Information: Infrared Radiation and its Applications
Infrared radiation plays a crucial role in many natural processes and technological applications.
- Heat Transfer: It is one of the primary modes of heat transfer, especially in a vacuum where convection and conduction cannot occur (like from the sun to the Earth).
- Thermal Imaging: Objects emit infrared radiation based on their temperature. Thermal cameras detect this radiation to create images showing temperature variations, used in fields like security, medicine, and building inspection.
- Remote Controls: Many remote controls use infrared light to transmit signals to devices like TVs.
- Heating Systems: Infrared heaters directly warm objects and people using radiant heat, rather than heating the air.
- Astronomy: Infrared telescopes can observe objects obscured by interstellar dust because infrared waves can penetrate dust clouds more effectively than visible light.
- Atmospheric Science: Infrared absorption and emission by greenhouse gases like water vapor and carbon dioxide are fundamental to the Earth's energy balance and the greenhouse effect.
Important Questions from Electromagnetic Waves
Consider the following statements about visible light, UV light and X-rays:
1. The wavelength of visible light is more than that of X-rays.
2. The energy of X-ray photons is higher than that of UV light photons.
3. The energy of UV light photons is less than that of visible light photons.
Which of the statements given above is/are correct?The wavelength of X-rays is of the order of
Which of the followings are the characteristics of electromagnetic waves?
1) They are elastic waves.
2) They can also move in a vacuum.
3) They have electric and magnetic components that are mutually perpendicular.
4) They move with a speed equal to 3 lakh meters per second.
Select the correct answer using the code given below:
Which of the following devices is based on the phenomenon of electromagnetic induction?
Which factor does NOT affect the magnitude of motional EMF in a conductor?
