Reflection & refraction of 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 does an investigation to determine the refractive index of a rectangular block of transparent material.

The student uses this equipment in their investigation.

• ray box

• rectangular transparent block

• protractor

• pencil

• paper

• ruler

This is the formula linking refractive index, angle of incidence and angle of refraction.

Describe a method to determine the refractive index of the material.

You may draw a diagram to help your answer.

The refractive index of the material is 1.2

State the formula linking the refractive index and the critical angle of a material.

Calculate the critical angle of this material.

critical angle =_........ degrees

Describe what is meant by the term total internal reflection.

The diagram shows a ray of light entering a prism made of the same material as the rectangular block used in the student’s investigation.

Use a protractor to determine the angle of incidence at the point where the ray of light is incident on side AB of the prism.

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

Complete the path of the ray of light.

The diagram shows two rays of green light entering a semicircular glass block.

Measure the angle of incidence and the angle of refraction for ray A as it enters the glass block.

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

angle of refraction =_........ degrees

State the formula linking refractive index, angle of incidence and angle of refraction.

Calculate the refractive index of the glass.

Complete the path of ray A until it crosses ray B.

Label the point where the rays cross with the letter F.

The refractive index of glass for red light is lower than for green light.

Explain what would happen to point F if red light were used instead of green light.

You may draw a diagram to help your answer.

The diagram shows two rays of light, A and B, incident on the boundary between air and water.

The refractive index of water is 1.33

Explain the paths of the two rays of light after they strike the boundary between air and water.

Include calculations in your answer and draw on the diagram to support your answer.

This question is about a filament lamp.

Which of these is the correct circuit symbol for a filament lamp?

The filament lamp emits visible light.

The table gives some statements about visible light.

Place ticks () in the boxes to show which statements are correct for visible light.

The diagram shows a ray of light from the filament lamp incident on the reflective side of a curved mirror.

Complete the diagram by drawing

the normal line where the ray is incident on the mirror.

the reflected ray of light.

The filament lamp is connected in a circuit with a switch and a battery of three cells.

When the switch is on, the filament lamp transfers 120 J of energy in a time of 3.0 minutes.

Each cell has a voltage of 1.5 V.

Calculate the current in the filament lamp.

A small plotting compass is placed near the wires in the circuit.

When the switch is turned on, the compass needle moves to a new position.

Give a reason why the compass needle moves.

Ground-penetrating radar (GPR) uses radio waves to detect changes in material underground.

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

GPR radio waves have a frequency of 170 MHz.

The speed of radio waves is 3.0 × 10⁸m / s.

Calculate the wavelength of the waves.

A radio wave passes through the ground and refracts at the boundary between soil and rock.

The diagram shows three wavefronts of the wave before and after refraction.

The wave is also reflected at the boundary between the soil and the rock.

Complete the diagram to show three wavefronts after the wave has been reflected at the boundary.

Explain why the radio waves passing through the rock have a smaller wavelength than the radio waves passing through the soil.

A glass prism can be used to refract light.

State the name of the piece of equipment used to measure angles.

Measure the angle of incidence and the angle of refraction for the light entering the prism.

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

angle of refraction =_........ degrees

State the formula linking refractive index, angle of incidence and angle of refraction.

Calculate the refractive index of the glass.

Two galaxies, A and B, emit red light with a reference wavelength of 630 nm.

An astronomer measures the wavelength of red light from galaxy A when the light arrives at the Earth.

The astronomer’s value for the wavelength is 645 nm.

Calculate the difference between the astronomer’s value for the wavelength and the reference wavelength of red light.

The change in wavelength happens because galaxy A is moving away from the Earth.

Calculate the speed of galaxy A.

[speed of light = 3.0 × 10⁸m / s]

Light from galaxy B has twice the redshift as light from galaxy A.

Galaxy B is twice as far away from Earth as galaxy A.

Explain how these observations support the Big Bang theory of the origin of the Universe.

This is a question about reflection.

Which diagram shows a light ray correctly reflected from a mirror?

Name the equipment needed to measure the angle of incidence on a ray diagram.

Light from a laser on the Earth reflects off special mirrors on the Moon.

The graph shows the data from a light sensor attached to the laser.

The first peak shows when the light leaves the laser and the second peak shows when the light has returned from the Moon.

Determine the time taken for the light to travel from the Earth to the Moon and back again.

The speed of light is 3.010⁵km/s.

Calculate the total distance travelled by the light from the laser.

[average speed = distance moved time taken]

Calculate the distance from the Earth to the Moon.

This question is about optical fibres.

Optical fibres use light waves for communication.

Which of these is a correct statement about waves?

A ray of light passes from air into a glass optical fibre.

Diagram 1 shows the path of the ray of light after it has passed through the boundary between air and the optical fibre.

Draw the path of the ray of light in air before it passed through the boundary.

Diagram 1

State the name of the wave behaviour responsible for the path of the ray of light as it passes from air into the optical fibre.

Diagram 2 shows the path of the ray of light as it travels through the optical fibre.

Explain the path of the ray of light as it travels through the optical fibre.

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.

The refractive index, n, of a material can be calculated using this formula.

A student uses this method to determine the refractive index of a material.

• draw around a semi-circular block of material

• shine a light ray towards the centre of the straight edge of the semi‑circular block

• use a pencil and a ruler to mark the positions of the incident ray and the refracted ray

• remove the block

• draw a normal where the ray was incident on the block

• measure the angle of incidence and angle of refraction

• calculate the refractive index using the formula

Repeat the method for different angles of incidence.

Name the independent variable in this investigation.

The table shows the student’s results for an angle of incidence of 40°.

Calculate the mean value for the angle of refraction.

mean angle =_........ degrees

Describe how the student could improve their method to get a more accurate value for the refractive index.

Diagram 1 shows a ray of light refracted by a transparent block of material.

Calculate the refractive index of this material.

State the formula linking critical angle and refractive index.

The refractive index of a different material is 1.7

Calculate the critical angle of this material.

critical angle =_........ degrees

Diagram 2 shows a ray of light travelling through an optical fibre.

The optical fibre is made of a material with a refractive index of 1.7

Explain the path of the ray in the optical fibre.

A student investigates the reflection of light by a plane mirror.

The student uses a ray box, a ruler, a pencil and a mirror.

Name the apparatus that can be used to measure angles during the investigation.

The diagram shows a ray of light directed to a point on the mirror.

Label the angle of incidence.

Measure the angle of incidence.

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

Complete the diagram to show the ray reflected from the mirror.

The diagram shows a fishing boat fitted with a high frequency sound wave emitter.

The boat is above some fish.

The high frequency sound waves travel from the emitter to the fish and then back to the emitter, where they are detected.

Name the wave behaviour that causes the sound waves to change direction when they reach the fish.

The table gives some data about the sound waves used.

Calculate the distance between the sound wave emitter and the fish.

High frequency sound waves decrease in amplitude as they travel through soft tissue in the human body.

The graph shows this decrease in amplitude for three different high frequency sound waves.

Estimate the distance travelled by a 2 MHz wave when its amplitude is 25% of its original value.

Describe what the graph shows about the penetrating ability of high frequency sound waves as they travel through soft tissue.

Diagram 1 shows a ray of violet light entering a prism.

Calculate the angle of refraction for the violet light.

angle of refraction =_........ degrees

State the formula linking refractive index, angle of incidence and angle of refraction.

Calculate the refractive index of the prism for violet light.

Give your answer to 2 significant figures.

Diagram 2 shows rays of red light and violet light entering the same prism.

Red light has a longer wavelength than violet light.

Deduce a possible relationship between the wavelength and the refractive index for colours of the visible spectrum.

A student does an experiment to determine the refractive index of a glass block.

The student places the glass block on a piece of paper and draws round the block with a pencil.

Name two additional pieces of equipment the student will need for his experiment.

The diagram shows the path of a ray of light as it travels towards and then through the glass block.

Draw the path of the ray of light when it leaves the glass block.

Draw the normal line at the point where the ray of light enters the glass block.

Determine the angle of incidence and the angle of refraction at the point where the ray of light enters the glass block.

State the formula linking refractive index, angle of incidence and angle of refraction.

Calculate the refractive index of the glass block.

A teacher suggests that a more accurate value for the refractive index can be found using a graphical method.

Design a method to obtain a value for the refractive index of the glass block using a graph.

You may draw a diagram to support your answer.

A student does an investigation to determine the refractive index of a block made from flint glass.

She directs a ray of red light at the block, as shown in diagram 1.

Some of the light is reflected from the surface of the block at point A.

On diagram 1, draw this reflected ray of light.

Use a protractor to determine the angle of incidence and the angle of refraction of the red light at point A on diagram 1.

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

angle of refraction =_........ degrees

State the formula linking refractive index, angle of incidence and angle of refraction.

Calculate the refractive index of the glass for red light.

Describe how the student could improve her investigation to obtain a more reliable value of the refractive index.

The student replaces the red light with a blue light.

Diagram 2 shows a ray of blue light directed at point A, at the same angle of incidence as the previous ray of red light.

The dashed lines on diagram 2 show the previous path of the ray of red light.

The refractive index of flint glass for blue light is higher than the refractive index of flint glass for red light.

Complete diagram 2 by drawing the path of blue light from point A until it passes into air.

This question is about wave behaviour.

The boxes give three types of wave behaviour and the diagrams give three examples of wave behaviour.

Draw one straight line from each wave behaviour to the example that best shows that behaviour.

Wave behaviour
Example

State two properties that all waves have in common.

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 atmospheric optical illusions.

A mirage is an optical illusion formed due to total internal reflection of light from the sky at the boundary between cold air and hot air.

Diagram 1 shows how a mirage is formed.

State the formula linking critical angle and refractive index.

The critical angle of the cold air at the boundary is 88.500°

Calculate the refractive index of the cold air.

Give your answer to 5 significant figures.

Diagram 2 shows a ray of light from the Sun.

The refractive index of the atmosphere is greater than the refractive index of space.

Complete the diagram by drawing the path of the ray of light through the atmosphere.

Diagram 3 shows a ray of light from the Sun when the Sun is directly overhead.

Explain why the ray of light does not change direction when it enters the atmosphere.

Explain why the wavelength of the light reduces when it enters the atmosphere.

Suggest why the Sun appears not to be circular when it is close to the horizon at sunset.

This question is about light.

Diagram 1 shows a light ray entering a glass prism.

Describe what happens to the light ray when it enters the prism at point A.

State the name of line XY.

State the formula linking critical angle and refractive index.

The refractive index for the glass in this prism is 1.6

Calculate the critical angle for the glass in this prism.

Complete Diagram 1 by continuing the path of the light ray from point B.

Diagram 2 shows a similar prism that is made from a material with a different refractive index.

The critical angle for the material of this prism is 55°

Complete Diagram 2 by continuing the path of the light ray.

A light ray travels from air into water.

Diagram 1 shows the direction of the light ray and the wavefronts in air.

Diagram 1

The refractive index of water is greater than the refractive index of air.

Complete diagram 1 by showing

● the wavefronts in the water

● the path of the light ray in the water

Explain what happens to the wavelength of light when it passes from air into water.

Diagram 2 shows what can happen when a light ray travelling in glass meets the boundary with air.

The wavefronts are not shown in this diagram.

Diagram 2

Add the normal to diagram 2.

Measure the angle of incidence in diagram 2.

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

The glass has a refractive index of 1.6

Calculate the critical angle of the glass-air boundary.

critical angle =_........ degrees

Explain the path of the light ray shown in diagram 2.