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.
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In simple terms, it means the change in frequency and wavelength of a wave because of the relative motion of the source with respect to the observer. The frequency observed f’ can be expressed by this equation:
f’ = f(v ± vₒ)/(v ∓ vₛ)
where:
– f’ is the observed frequency,
– f is the source frequency,
– v is a constant speed of propagation of the wave,
– vₒ is the velocity of the observer,
– vₛ is the velocity of the source.
Once again, though, since wave speed remains constant in a given medium, firmly speaking there must also be a change in wavelength λ’ for a change in frequency f’ to occur regarding the wave equation:
v = fλ
So the Doppler effect is that the frequency and wave have been destroyed, with speed being uniform.
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