Need help from an expert?
The world’s top online tutoring provider trusted by students, parents, and schools globally.
Apparent frequency is the frequency observed by an observer, while actual frequency is the frequency emitted by the source.
In the context of the Doppler effect, the apparent frequency and the actual frequency can differ significantly. The Doppler effect refers to the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. This effect is commonly observed with sound waves, but it also applies to light waves and other types of electromagnetic radiation.
The actual frequency, also known as the emitted frequency, is the frequency at which a wave, such as sound or light, is originally produced by its source. For instance, if a car horn honks at a certain pitch, that pitch represents the actual frequency of the sound wave produced by the horn. This frequency does not change regardless of where the source is or how fast it's moving.
On the other hand, the apparent frequency is the frequency as measured by an observer. This frequency can change based on the relative motion between the observer and the source of the wave. If the source and the observer are moving closer together, the apparent frequency will be higher than the actual frequency. Conversely, if they are moving apart, the apparent frequency will be lower.
For example, as a police car with a blaring siren approaches you, the pitch of the siren seems to increase. This is because the waves are reaching you more frequently, hence the apparent frequency is higher. As the car passes you and moves away, the pitch seems to decrease because the waves are now reaching you less frequently, making the apparent frequency lower. In both cases, the actual frequency of the siren remains the same.
In summary, the actual frequency is the original frequency of a wave as produced by its source, while the apparent frequency is how frequently the wave is observed to reach an observer, which can change based on the relative motion between the observer and the source. This difference between the two is the basis of the Doppler effect.
Study and Practice for Free
Trusted by 100,000+ Students Worldwide
Achieve Top Grades in your Exams with our Free Resources.
Practice Questions, Study Notes, and Past Exam Papers for all Subjects!
The world’s top online tutoring provider trusted by students, parents, and schools globally.