Question

Radio waves are

• A. produced by hot bodies
• B. in the frequency range 10⁹ Hz to 10¹² Hz
• C. suitable for radar systems
• D. used in cellular phones to transmit voice communication
• E. used to kill germs in water purifiers

Answer 1

The Correct Option is D

Radio waves are electromagnetic waves that have frequencies in the range of \( 10^3 \, \text{Hz} \) to \( 10^{12} \, \text{Hz} \). They are widely used for various communication systems, including AM/FM radio, TV signals, and cellular phones. In cellular phones, radio waves are used to transmit voice communication by modulating the voice signal onto a carrier wave.
Thus, the correct answer is that radio waves are used in cellular phones to transmit voice communication.

The correct option is (D) : used in cellular phones to transmit voice communication

Answer 2

Let's analyze each statement about radio waves:

1. Produced by hot bodies 
→ Not typically. Infrared and visible light are more associated with thermal radiation.

2. In the frequency range 10⁹ Hz to 10¹² Hz 
→ This range corresponds more to microwaves and far-infrared, not radio waves.
Radio waves typically range from 10³ Hz to 10⁹ Hz.

3. Suitable for radar systems 
→ Yes, radar uses radio waves and microwaves.

4. Used in cellular phones to transmit voice communication 
→ Yes, cellular communication often uses radio and microwave frequencies.

5. Used to kill germs in water purifiers 
→ Incorrect. UV rays, not radio waves, are used for sterilization.

Correct statements:
✔ Suitable for radar systems
✔ Used in cellular phones to transmit voice communication