Transverse and longitudinal waves

This question is about light.

Light is an example of a transverse wave.

Describe a transverse wave.

You may draw a diagram to help your answer.

Diagram 1 shows a ray of light in a section of optical fibre.

Diagram 1

The ray of light is incident at the boundary between the optical fibre and air.

The ray of light reflects at the boundary.

Complete diagram 1 by drawing the reflected ray of light.

Explain why no light leaves the optical fibre when the light reflects at the boundary between the optical fibre and air.

Diagram 2 shows a different ray of light, incident on the boundary between water

Using diagram 2, show that the refractive index of water is approximately 1.3

A student uses a ripple tank to investigate water waves.

Diagram 1 shows the ripple tank when viewed from the side.

A dipper moves up and down to produce waves on the surface of the water in the container.

The waves on the surface of the water are transverse.

State what is meant by a transverse wave.

You may draw a diagram to help your answer.

Diagram 2 shows the surface of the ripple tank, at an instant in time, when viewed from above.

Diagram 2

The dipper produces circular waves on the surface of the water.

1 cm in diagram 2 is equal to 2 cm in the laboratory.

Use the diagram to measure the wavelength of the water waves.

The dipper moves up and down with a frequency of 15 Hz.

Calculate the speed of the waves.

The student then makes the dipper move horizontally to the right at constant speed.

The dipper continues to move up and down with a frequency of 15 Hz.

Diagram 3 shows the surface of the ripple tank, at an instant in time, when viewed from above.

Diagram 3

Explain how the frequency of the waves arriving at point X compares with the frequency at which the dipper moves up and down.

The diagram shows two whales in the sea.

Some species of whale communicate with sound signals and visual signals.

Describe the difference between the motion of particles in a transverse wave and the motion of particles in a longitudinal wave.

You may use a diagram to help your answer.

Whale A makes a sound with a constant frequency. This sound is detected by whale B.

When whale A swims towards whale B, the frequency of the sound detected by whale B increases.

This is known as the Doppler effect.

Explain how the Doppler effect causes the frequency of sound detected by whale B to increase.

Visible light from the Sun reaches whale B.

The wavelength of this light is 5.410^–7m.

Calculate the frequency of this light.

[speed of light = 3.0×10⁸m/s]

The photograph shows an x-ray image of a person’s knee. The person has had part of their knee replaced.

X-rays are part of the electromagnetic spectrum.

All electromagnetic waves are transverse waves and transfer energy.

State another property that all electromagnetic waves have in common.

State a harmful effect of excessive exposure to x-rays.

Describe the difference between transverse waves and longitudinal waves.

You may draw a diagram to help your answer.

The diagram shows a part of the knee called the patella. The patella has been removed from a person’s knee.

The patella is a small, irregularly shaped bone that is denser than water.

Describe how to find the mass and the volume of the patella bone.

A scientist finds the volume and mass of a patella.

The mass of the patella is 17 g.

The volume of the patella is 13 cm³.

Calculate the density of the patella.

Give your answer to 2 significant figures.

density =_........ g / cm³

An ultrasonic distance-measuring device can be used to measure the length of a room.

The device emits a pulse of sound with a frequency of 40 kHz.

The device also emits a bright beam of red visible light.

Explain what is meant by a frequency of 40 kHz.

A sound wave from the device travels at 345 m / s.

State the formula linking wave speed, frequency and wavelength.

Calculate the wavelength of the sound wave.

The device emits a sound wave.

The sound wave travels to the wall, reflects back to the device and is received by the device.

The distance from the device to the wall is 2.35 m.

Calculate the time between the sound wave being emitted and received by the device.

Suggest why the device emits visible light.

Sound waves and light waves can have different frequencies and wavelengths.

Describe three other differences between sound waves and light waves.

You may draw diagrams to support your answer.

Diagram 1 shows water waves just before they reflect off the side of a stationary boat.

Draw the normal at the point where the direction of travel of the waves meets the side of the boat.

Measure the angle of incidence of the water waves.

angle of incidence =_........ degrees

Complete the diagram to show the wavefronts after they reflect off the side of the boat.

The boat starts to move, creating its own waves on the surface of the water.

Surface water waves are transverse.

Describe the difference between transverse waves and longitudinal waves.

Diagram 2 shows the boat moving towards an observer.

Explain why the frequency of the water waves measured by the observer is larger than the frequency of the water waves created by the boat.

Wi-Fi signals are electromagnetic waves that can be transmitted at frequencies of 2.4 GHz and 5.2 GHz.

State a similarity of the Wi-Fi signals at 2.4 GHz and 5.2 GHz.

The two Wi-Fi signals have different frequencies.

State another difference between the Wi-Fi signals.

State the formula linking speed, frequency and wavelength.

Calculate the wavelength of Wi-Fi signals transmitted at 5.2 × 10⁹Hz.

[speed of light = 3.0 × 10⁸m / s]

Which type of wave is a Wi-Fi signal?

Describe the difference between a transverse wave and a longitudinal wave. You may draw a diagram to help your answer.

The photograph shows a security camera.

The camera detects light waves and sound waves.

State two differences between light waves and sound waves.

The camera detects infrared waves, which allow the camera to record videos in the dark.

Which of these electromagnetic waves has a longer wavelength than infrared waves?

Which of these is another use for infrared waves?

Which of these is a harmful effect of infrared waves?

The grid shows the oscilloscope trace for a quiet, low‑pitch sound wave.

The security camera has an alarm that produces a loud, high‑pitch sound.

On the grid, draw a trace to represent the sound wave produced by the alarm.

When a meteor explodes, light waves and sound waves are produced at the same time.

State the formula linking average speed, distance moved and time taken.

A person standing 1860 m away from the site of a meteor explosion hears the sound of the explosion 5.6 s later.

Calculate the speed of sound in air.

A scientist stands a long way from the meteor explosion.

Explain why he hears the explosion at a different time to when he sees it.

Sound is a longitudinal wave.

Describe what is meant by the term longitudinal wave.

In 2013, a meteor exploded above Russia.

Just before the meteor exploded, it was travelling at a speed of 19.2 km/s.

The mass of the meteor was estimated to be 1.25 × 10⁷kg.

State the formula linking kinetic energy, mass and speed.

Calculate the energy in the kinetic store of the meteor just before the meteor exploded.

This question is about sound waves.

Sound is an example of a type of wave.

State the name of this type of wave.

The speed of sound in liquids is greater than the speed of sound in gases.

Describe the arrangement of particles in liquids and in gases.

You may use diagrams to help your answer.

Suggest why the speed of sound in liquids is greater than the speed of sound in gases.

A buzzer is an electrical device that produces sound.

The frequency of sound produced by the buzzer is 1400 Hz.

State the formula linking speed, frequency and wavelength of a wave.

Sound travels at a speed of 340 m/s in air.

Calculate the wavelength of the sound wave from the buzzer.

Two students use this method to investigate sound from a moving source.

Student A connects a piece of string to the buzzer.

She spins round so that the buzzer moves in a horizontal circular path.

● she spins round at a slow speed

● she then spins round at a high speed

Student B stands several metres away from student A.

The sound heard by student A is different to the sound heard by student B.

Discuss the differences in the sounds heard by student A and student B.