AP Physics 1 : Electricity and Waves

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #31 :Waves

What is the wavelength of a radio station that broadcasts at 92.9MHz?

Possible Answers:

Correct answer:

Explanation:

We need to know the speed of light, which is:

We can use this to calculate the wavelength of any electromagnetic wave if we know the frequency, using the equation:

If you're unsure of how to come about this equation, you should be able to derive it by looking at your units. Use our given values to solve for the wavelength:

Example Question #1 :Wavelength And Amplitude

A wave with a speed ofhas a frequency of 30Hz. What is the wavelength?

Possible Answers:

Correct answer:

Explanation:

Since the wave has a frequency of 30Hz, we know it completes 30 cycles every second. As its velocity is, we also know that in that second, the wave has moved 10m. Dividing the total distance, 10m, by the number of cycles, 30, we get the number of meters travelled in each cycle which is the wavelength:

Example Question #1 :Wavelength And Amplitude

Given the speed of a wave asand the wavelength of 0.2m, find its frequency.

Possible Answers:

Correct answer:

Explanation:

Speed is frequency times wavelength. So the frequency must be speed divided by wavelength. In this case:

This makes sense as in one second, the wave will have travelled 15m. Each meter is 5 cycles, so over the distance the wave has travelled in one second, it has completedcycles.

Example Question #31 :Waves

An equation of a wave is given by the following formula:

Here,is given in meters andis given in seconds. Determine the period of the wave in seconds.

Possible Answers:

Correct answer:

Explanation:

A trigonometric equation given by the following formula

Here,is given in meters,is given in Hertz,is given in seconds, andis given in meters. The period is given by:

In our case:

Example Question #2 :Wavelength And Amplitude

The music we listen to on the radio is transmitted in the form of radio waves. You might have seen that a radio station on FM is broadcasted in, which is.

What is the wavelength of a radio wave if it's being transmitted on a frequency of?

Possible Answers:

Correct answer:

Explanation:

Radio waves travel at the speed of light. The relationship between wavelength, frequency, and wave speed is

, whereis the wavelength andis the frequency.

In our case,

.

因此,

Example Question #36 :Waves

An original signal's frequency is halved by a resistor, and no other part of the wave is effected. Determine the change in the amplitude of the signal.

Possible Answers:

The amplitude is unchanged

The amplitude is doubled

The amplitude is halved

The amplitude is quadrupled

Correct answer:

The amplitude is unchanged

Explanation:

Amplitude refers to the strength of a wave and has no relation to its frequency. Frequency would only affect the period and phase, but not the amplitude.

Example Question #1 :Frequency And Period

What is the wavelength of awave if its velocity is?

Possible Answers:

Correct answer:

Explanation:

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 :Frequency And Period

A pendulum of lengthwith a ball of massis released at an angle远离平衡点. Which of the following adjustments will result in an increase in frequency of oscillation?

Possible Answers:

Increasing the initial angle

Increasing the ball's mass

Increasing the length

Decreasing the ball's mass

Decreasing the length

Correct answer:

Decreasing the length

Explanation:

For a pendulum on a string, the period at which it oscillates is:

Period is the reciprocal of frequency.

Calculate the frequency of oscillation.

The only parameter that the frequency depends on is the length. Decreasing length increases frequency.

Example Question #1 :Frequency And Period

The wavelength of a ray of light travelling through a vaccuum is. What is the period of this wave?

Possible Answers:

Correct answer:

Explanation:

In this question, we're given the wavelength of light in a vaccuum. Since we know that the speed of light in a vaccuum is equal to, we can first calculate the frequency of the light, and then use this value to calculate its period.

To begin with, we'll need to make use of the following equation to solve for frequency.

Then, using this value, we can calculate the period by noting that the period is the inverse of frequency.

And for completion's sake, it is worth noting that the period refers to the amount of time it takes for one wavelength to pass, which in this case is a very, very small fraction of a second!

Example Question #1 :Frequency And Period

Waves are hitting the side of a pier in a regular fashion. During 1 minute,waves that hit the side of the pier. Calculate the periodof the waves during this time in seconds.

Possible Answers:

Cannot be determined.

Correct answer:

Explanation:

In order to calculate the period, we need to find the frequency,, at which the waves hit the pier. We are told thatwaves hit within a窗口。因此,

. We can then calculate the periodfrom this information.

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