एक बंद ऑर्गन पाइप और एक खुले ऑर्गन पाइप को समान मूल आवृत्ति पर ट्यून किया जाता है। उनकी लंबाइयों का अनुपात क्या है?

Consider the following applications: I. Estimating the speed of an aircraft or ship by means of reflected waves II. Inferring the expansion of the universe through shift in spectral lines III. Determining the age of geological or fossil-bearing material through radiometric methods IV. Measuring blood flow in arteries using medical imaging techniques How many of the above involve the use of the Doppler effect?

A sound wave travels from air into water. How do its frequency, speed, and wavelength change as it crosses the boundary?