Question

Radar waves are sent towards a moving airplane and the reflected waves are received. When the airplane is moving towards the radar, the wavelength of the wave

• A. decrease
• B. increase
• C. remains the same
• D. sometimes increase or decrease

Hint:

The Doppler effect causes the wavelength to decrease when the source is moving towards the observer.

Answer 1

The Correct Option is A

Step 1: Doppler Effect.
When a source of waves (in this case, the airplane) moves towards the observer (the radar), the wavelength of the waves decreases. This is due to the Doppler effect.

Step 2: Conclusion.
Therefore, the correct answer is option (A).

Final Answer: \[ \boxed{\text{(A) decrease}} \]