The Doppler effect causes a change in

The Doppler effect is the change in frequency or wavelength of a wave due to the motion of the source or observer. When the source moves toward the observer the frequency increases and the wavelength decreases. When it moves away the frequency decreases and the wavelength increases.

Oscillations in Class 11 Physics cover periodic motion where an object moves to and fro about a fixed point. This chapter explains simple harmonic motion, time period, frequency, and amplitude. It includes concepts like damped and forced oscillations and resonance. Understanding oscillations is essential for CBSE Exam 2024-25 as it forms the basis for waves.