Question
Physics Question on Waves
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
Answer
decrease
Explanation
Solution
Here, vs=0 and vL is negative where vs is velocity of source and vL is velocity of listener (aeroplane) If apparent frequency is v′ and v is actual frequency, then v′=vv−(−vL)v =vv+vLv i.e., v′>v So, apparent frequency will increase, it means apparent wavelength will decrease.