Transverse & longitudinal waves

The diagram shows a photograph of the pattern of water waves, drawn to scale.

A student measures the wavelength of the water waves with a ruler.

Which method will not improve the accuracy of the student’s measurement?

A Place the ruler at a right angle to the wavefront.

B Measure the length of 5 complete waves and divide this length by 5.

C Place the ruler flat on the photograph and read the scale at right angles from above.

D Use a longer ruler to measure one wavelength.

A sound engineer records sound waves from loudspeakers in four different locations A, B, C and D in a concert hall.

An oscilloscope is used to display the sound waves produced at each location. The settings on the oscilloscope remain the same for each location.

At which location does the sound wave have the greatest amplitude ?

Tick (✓) one box.

One of the sound waves recorded has a frequency of 250 Hz.

The speed of sound in the concert hall is 340 m / s.

Calculate the wavelength of this sound.

Use the equation: wave speed = frequency wavelength

The engineer places a candle in front of a loudspeaker.

The loudspeaker produces a low frequency sound.

Complete the sentences to explain why the candle flame vibrates from side to side but does not blow out.

Use words from the list.

electromagnetic longitudinal particles transverse waves

The flame vibrates from side to side because sound waves are........ waves.

Air........ vibrate but do not travel through the flame.

The frequency, wavelength and speed of the waves can be changed.

State the unit for each of the variables.

The student takes a photograph of the wave pattern projected onto the white paper.

Fig. 13.2 shows a diagram of the photograph.

Fig. 13.2

Describe how the student uses Fig. 13.2 to obtain an accurate value for the wavelength of the wave.

You can draw on Fig. 13.2 to support your answer.

The student lifts the ripple tank at one end so that the water is deeper at one end of the ripple tank than at the other end.

The student uses the motor and paddle to produce waves and takes a photograph of the wave pattern projected onto the white paper.

Fig. 13.3 shows a scale diagram of the photograph.

Fig. 13.3

Describe and explain how the speed of the waves changes as the waves travel from the deep end of the ripple tank to the shallow end in Fig. 13.3.

Use the relationship between wave speed, frequency and wavelength in your explanation.

13* A student investigates the speed of a water wave using this equipment.

Plastic tray
Ruler
Stopwatch

The student lifts one side of the plastic tray and drops it to make a wave.

Describe how the student can use this equipment to measure the speed of a water wave.

In your answer you should include:

• the measurements they should take

• the variables they need to keep constant

• any precautions they should take to obtain accurate and precise results.

This question is about electromagnetic waves.

Electromagnetic waves are transverse waves.

Describe what a transverse wave is.

You can label the diagram of a transverse wave to help explain your answer.

A radio wave has a frequency of 7 500 kHz and a wavelength of 40 m.

Calculate the speed of this radio wave.

Use the equation: wave speed = frequency wavelength

Give your answer in metres per second.

Speed =........ m / s

The table shows some different radio waves.

What is the relationship between frequency range and wavelength?

Use the table.

Which type of radio wave has a frequency of 15 MHz and a wavelength of 20 m?

Tick (✓) one box.

High frequency radio waves are similar to microwaves.

Suggest how high frequency radio waves can harm the human body.

Complete the sentence about high frequency radio waves.

High frequency radio waves are more / less dangerous than microwaves.

Suggest a reason for your answer.

In 1709, William Derham measured the speed of sound using a cannon.

A cannon contains an explosive called gunpowder. When a cannon is fired, the gunpowder acts as a fuel and is ignited. A cannonball moves upwards through the air.

Describe the change in energy stores when a cannon is fired.

Derham climbed a church tower to look for the flash from the cannon and to hear its bang.

The cannon was fired a long distance away from the church.

Derham measured the distance between the cannon and the church.

Describe how Derham used the firing of the cannon to work out the speed of sound.

Why is it important that the cannon is a long distance away?

Derham calculated the speed of sound using an old unit of distance called the Parisian foot.

One value he calculated for the speed of sound was 1122 Parisian feet per second.

1 Parisian foot = 32.5 cm

Calculate Derham’s value for the speed of sound in m / s.

Speed =........ m / s

Today, scientists know the speed of sound is 1056 Parisian feet per second.

The percentage difference between Derham’s value and today’s value for the speed of sound is calculated using this equation:

Use this equation to evaluate the accuracy of Derham’s value for the speed of sound.

Fig. 12.1 shows air particles in a room.

Fig. 12.1

A scientist produces a sound wave in the room using a vibrating tuning fork.

Describe what happens to the air particles when the sound wave travels through the room as a longitudinal wave.

You can draw on Fig. 12.2 to support your answer.

Fig. 12.2

The diagram shows a sound wave.

Write the letter B, C or D in the correct boxes to label the diagram.

One has been done for you.

Which type of wave is a sound wave? Tick (✓) one box.

A student downloads a physics app to their mobile phone. The app contains an ‘acoustic stopwatch’.

The app works like this:

• When the microphone detects a loud sound, the acoustic stopwatch starts.

• When the microphone detects the next loud sound, the acoustic stopwatch stops.

Describe how the student can use the app to measure the speed of sound. Include the names of other equipment that the student will need to use.

Another student suggests using this stopwatch.

Suggest why the ‘acoustic stopwatch’ on the mobile phone app is an improvement on using this stopwatch.

The wavelength of a sound wave is 0.55 m.

The speed of sound in air is 330 m / s.

Calculate the frequency of the sound wave.

Use the Equation Sheet.

Describe the motion of air particles in a sound wave. You may include a labelled diagram.

Table 17.1 shows the results for one student.

Table 17.1

The wavelength of the sound = 4 × the length of the tube above the water.

Calculate a value for the speed of sound using this student’s results.

Use the Equation Sheet.

Speed of sound =........ m / s

Table 17.2 shows the results for the group of students.

Table 17.2

The quality of these results can be judged using percentage uncertainty.

The percentage uncertainty in an experimental value is given by the equation.

Calculate the percentage uncertainty in the students’ results from Table 17.2.

The speed of sound at 20 °C is 343 m / s.

Evaluate the precision and accuracy of the results in Table 17.2.

Which statement improves the accuracy of the results?

Tick (✓) one box.

Which statement describes a systematic error in the experiment?

Tick (✓) one box.

This question is about waves.

Two students are watching a tap dripping water into a bowl. As the water drips, it makes waves in the bowl, as shown in Fig 13.1.

The students want to calculate the frequency of the waves in the bowl.

Define frequency.

In 10 seconds, 10 waves are made in the bowl.

State the frequency of the waves.

The students want to measure the wavelength of the water’s waves.

Describe a way for them to do this accurately.

Storms can produce thunder and lightning.

The speed of light is 3 × 10⁸ m / s.

Estimate how many times greater the speed of light is than the speed of sound.

A storm is 1340 m away.

A student sees the lightning and then hears the thunder 4 s later.

Calculate the speed of sound.

Use the equation: distance travelled = speed × time

Speed of sound =........ m / s

The speed of sound can be worked out using two different methods.

Method 1: Clapping your hands and timing the echo from a wall.

Method 2: Measuring the time to hear the thunder after seeing the lightning.

Which method is better?

Explain your answer.

Some waves are transverse. Some waves are longitudinal.

Which row in the table is correct?

Two students are making waves using a dripping tap.

The water droplets create waves in the water in a bowl.

Describe the change in energy stores as a water droplet

• falls from the tap:........

• lands in the water in the bowl:........

The students count the number of droplets hitting the water in the bowl.

In 20 seconds, 5 droplets hit the water in the bowl.

Calculate the frequency of the waves produced.

How can the students tell that the water waves travel but the water does not?

One of the students says, ‘the temperature of the water in the bowl increases when the water drips into it’.

• 1 droplet of water transfers 5.04 × 10⁻⁴ J of energy as it lands in the bowl.

• The bowl contains 3 kg of water.

• The specific heat capacity of water is 4200 J / kg °C.

Calculate the temperature rise of the water in the bowl when 1 droplet of water lands in it.

Use an equation from the Data Sheet to help you.

In 1847, James Joule did experiments at the bottom of a waterfall.

He was unable to measure the temperature rise of the water.

Suggest two reasons why.

Electromagnetic waves have similar properties.

Use these words to complete the sentences:

You can use each word once, more than once, or not at all.

Acceleration Frequency Longitudinal

Sound Speed Transverse Wavelength

Electromagnetic waves are …………………………. waves.

Electromagnetic waves travel with the same …………………………. in space.

A student wants to work out the speed of water waves in a ripple tank. Fig. 13.1 shows the apparatus the student uses.

Name the two extra pieces of apparatus she will need to work out the speed of the waves.

This question is about sound, light and water waves.

State one difference between sound waves and light waves.

In Fig. 13.1, a student makes waves in a tray of water. He places a cork at position A.

Fig. 13.2 shows a free-body force diagram for the cork.

At position A in Fig. 13.1, the cork starts to move up.

Use the free-body force diagram to explain why.

Explain how this experiment shows that the wave travels but not the water.

A teacher uses a signal generator to produce a sound wave.

Fig. 13.3 shows the sound wave on the oscilloscope screen.

1 cm represents 0.005 s on the horizontal scale.

Calculate the period of the sound wave.

Calculate the frequency of the sound wave.

Fig. 13.4 shows the experiment a teacher does to measure the speed of sound.

She uses two microphones and a speaker.

• The speaker is connected to a signal generator.

• The speaker emits sound with a frequency of 1200 Hz.

• Microphone 2 is moved 0.29 m to the right of microphone 1.

• The traces on the oscilloscope screen are one wavelength apart.

Calculate the wave speed of sound.

Wave speed =........ m / s

Suggest how this experiment can be improved.

The speed of sound can also be calculated using echoes and a large wall.

Explain how.

A transverse wave and a longitudinal wave travel in the direction shown by the arrow.

The table shows how the particles in these waves vibrate as the waves travel.

Which row of the table is correct?

The graph shows how the height of a water wave changes with distance.

The water wave has a wavelength of 6 m.

Describe how the graph shows this.

The frequency of the water wave is 0.5 Hz.

Calculate the speed of this water wave.

Answer =........ m / s

A group of students use a ripple tank, a metre ruler and a stopwatch.

They draw a diagram of this equipment.

Explain how this equipment is used to measure the frequency of water waves.

The graph shows how the height of a water wave changes with distance.

The water wave has a wavelength of 6 m.

Describe how the graph shows this.

The frequency of the water wave is 0.5 Hz.

Calculate the speed of this water wave.

Answer =........ m / s

A group of students use a ripple tank, a metre ruler and a stopwatch.

They draw a diagram of this equipment.

Explain how this equipment is used to measure the frequency of water waves.