When a source is moving towards a stationary observer, the apparent change in frequency will be:

Explanation

Option A: The apparent change in frequency will be greater than the original frequency when a source is moving towards a stationary observer. This is because the waves from the source are compressed as they approach the observer, which increases the frequency of the waves.The opposite is true when the source is moving away from the observer. In that case, the waves are stretched out, which decreases the frequency of the waves.This is known as the Doppler effect. It is a phenomenon that occurs when there is a relative motion between a source of waves and an observer. The Doppler effect can be observed with sound waves, light waves, and other waves. Option B: This is not possible. The frequency of the waves from the source will always change when there is a relative motion between the source and the observer. The only way that the frequency of the waves would remain the same is if the source and the observer were moving at the same speed in the same direction. Optio C: This is possible. When a source is moving away from a stationary observer, the waves from the source are stretched out as they move away from the observer, which decreases the frequency of the waves. This is known as the redshift. The redshift is a phenomenon that occurs when there is a relative motion between a source of waves and an observer, and the source is moving away from the observer. The redshift can be observed with light waves, and it is used to measure the expansion of the universe. Option D: This is not possible. The frequency of the waves from the source will always change when there is a relative motion between the source and the observer. The only way that the frequency of the waves would not change is if the source and the observer were not moving relative to each other.