All SAT II Physics Resources
Example Questions
Example Question #1 : Velocity, Frequency, And Wavelength
What is the wavelength of a wave if its velocity is ?
The relationship between wavelength and velocity is given by the equation;
The question gives us the velocity of the wave and its frequency. Using these values, we can solve for the wavelength.
Example Question #1 : Velocity, Frequency, And Wavelength
What best describes how a wave is affected when it travels from one medium to another medium?
The wave speed changed, but the frequency remains the same
Both speed and frequency change
The wavelength does not change
The frequency changes, but the speed remains the same
Neither speed not frequency change
The wave speed changed, but the frequency remains the same
It is a property of waves that the frequency remains constant and speed changes as it passes from one medium to another.
Example Question #1 : Waves
A train blows its whistle as it approaches a station at . If the sound emitted by the whistle has a frequency of , what is the frequency of the sound heard by the people at the station?
Wave frequency is distorted when the observer or source is in motion based on the Doppler effect. The equation for the Doppler effect is:
Terms in the numerator are summed if the observer moves toward the source. Terms in the denominator are summed if the source is moving away from the observer.
In this question, the train (source) is moving toward the observer. This means that the denominator terms will be subtracted. The velocity of the observer is zero, giving us our final equation:
Use the given values for the emitted frequency, velocity of the train, and speed of sound to solve this equation.
Example Question #1 : Optics, Waves, And Quantum
A dog is stationary in someone's front yard and barks at a frequency of . Which of the following could explain why an observer hears a frequency of ?
The observer is moving away from the dog
Both the dog and the observer have the same velocity
Both the dog and the observer have the same acceleration
The observer is moving towards the dog
The observer is traveling in circular path with the dog at the center of the circle
The observer is moving towards the dog
The doppler effect states that the observed frequency depends on the frequency produced, and the relative velocities of the observer and sound source:
To increase the observed frequency the sound source and the observer must be moving towards each other. Since the dog is stationary, therefore the observer must be moving towards the dog.