Refractive index & Snell's law

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.

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.

The diagram shows the path of a ray of light.

Measure the angle of incidence for the ray at point K.

Which of these is the angle of incidence?

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

The block has a refractive index of 1.52

Use the formula to show that the angle of refraction is about 30° for the ray at point K.

The refractive index of the block is 1.52

Calculate the critical angle of the block.

State what happens to the ray at point L.

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.

Describe an experiment to determine the refractive index of a glass block.

In your answer you should include

• a labelled diagram

• the apparatus needed

• the method used

Give two uses of total internal reflection.

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.

The diagram shows a ray of light travelling from air into glass.

Use a protractor to determine the angle of refraction.

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

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

Calculate the refractive index of this glass.

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.