Visible light & colour

Some people wear glasses when they are reading.

Figure 6 shows parallel rays of light passing through a convex lens from a pair of reading glasses.

What name is given to point X in Figure 6 ?

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Light changes direction as it enters the lens.

What is the name of this process?

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Which of the following is the shape of a convex lens?

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Figure 7 shows a lens forming a magnified image of an object.

Measure the image height and the object height in Figure 7.

Calculate the magnification produced by the lens.

Use your answers to Question 05.4 and the equation:

Why does magnification have no unit?

Tick (✓) one box.

Some reading glasses contain lenses made from blue glass.

The blue glass acts as a filter.

Describe what happens to white light incident on colourless glass and white light incident on blue glass.

Figure 10 shows the wavelengths of some types of electromagnetic radiation.

Suggest one piece of equipment that can be used to detect infrared radiation.

Which of the following values is a wavelength of red light?

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Figure 10 is repeated below.

The eyes of a bee can detect electromagnetic radiation with wavelengths between 300 nm and 600 nm.

Give two ways the radiation detected by the eyes of a bee is different from the radiation detected by human eyes.

Complete the sentences.

Choose the answers from the box.

When sunlight shines on a red flower, the red light

All other colours of light shining on the red flower

A gardener looks at a red flower through a green filter.

How does the flower appear to the gardener?

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The leaves of the plant reflect light.

The leaves have a rough surface.

What type of reflection happens at the leaf surface?

A student investigated the refraction of light through a glass block. Figure 14 shows the ray box used. The student aimed the beam of light from the ray box towards a glass block. The student measured the angle of incidence at the point where the light entered the glass block.

Why is using a wide beam of light less likely to give accurate results than using a narrow beam? Tick (✓) one box.

Figure 15 shows the beam of light incident on the glass block.

Complete Figure 15 to show the path taken by the beam of light through the glass block and back into the air.

Figure 16 shows the protractor used by the student.

What is the resolution of the protractor? Tick (✓) one box.

For one angle of incidence the student measured the angle of refraction three times. The three measurements were: 35° 31° 33° Calculate the mean angle of refraction.

The student placed a red filter in front of the white beam of light. Only red light passes through the filter.

Complete the sentence.

When white light is incident on the red filter, all colours except for red are

Use the Physics Equations Sheet to answer questions 06.6 and 06.7.

Light has a wave speed of 3.0 × 10⁸ m/s in air. The frequency of the red light is 4.0 × 10¹⁴ Hz. Calculate the wavelength of the red light in air.

A student investigated the behaviour of light. The student used a mirror with a smooth surface to investigate reflection. Figure 17 shows the equipment used.

What name is given to reflection from a smooth surface?

The student measured the angle of reflection for different angles of incidence. Table 2 shows the results.

What conclusion can be made from the results in Table 2 ?

What type of error caused the variation in the results for the angle of reflection? Suggest one cause of this error.

The student also investigated the refraction of light.

Figure 18 shows the path of a ray of light through a glass block.

Why has refraction not occurred?

The student measured the angle of refraction for different angles of incidence. Figure 19 shows the protractor used.

When the angle of incidence was 10° the student measured the angle of refraction four times. The student recorded the measurements as: 6.0° 6.3° 6.4° 5.8° Explain why the student should not have recorded these results when using the protractor in Figure 19 to make the measurements.

Figure 20 shows what happens to wave fronts as they pass across the boundary between air and glass.

Explain in terms of the wave fronts, why refraction happens at the boundary between air and glass.

Ultraviolet and visible light are both parts of the electromagnetic spectrum.

How does the speed of ultraviolet in a vacuum compare to the speed of visible light in a vacuum?

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Figure 9 shows parts of the electromagnetic spectrum.

Which letters represent the positions of ultraviolet and visible light in the electromagnetic spectrum?

Table 3 shows the range of wavelengths for different types of ultraviolet.

Determine which type of ultraviolet shown in Table 3 has the largest range of wavelengths.

To gain full marks you must calculate the range of wavelengths for each type of ultraviolet.

Figure 10 shows how different types of ultraviolet are absorbed by the ozone layer in the Earth’s atmosphere.

Table 4 shows the relative ionising power from each type of ultraviolet.

Explain the importance of the ozone layer in reducing the risk to people from all types of ultraviolet.

Use Figure 10 and Table 4.

The Sun emits visible light.

A student concludes that visible light is not absorbed by the ozone layer.

Give one piece of evidence that shows the student’s conclusion is correct.

Figure 11 shows white light incident on a colour filter.

Complete the sentence.

Choose the answers from the box.

Lenses are used to form images of objects.

Figure 6 shows how a concave lens forms an image of an object.

The image of the object in Figure 6 is upright. Give two other words that describe the image.

Figure 7 shows an object near to a convex lens. Complete the ray diagram to show how the image is formed. Use an arrow to represent the image.

The position of an image formed by a convex lens varies with the distance between the object and the lens. Figure 8 shows the results of a student’s investigation using a convex lens.

Describe how the distance of the image from the lens decreases as the distance between the object and the lens increases.

The student measured the distance from the image to the lens four times. The distance between the object and the lens did not change. The 4 measurements from the image to the lens were: 1.9 cm 1.7 cm 2.2 cm 1.4 cm Calculate the uncertainty in the measurements.

Figure 9 shows a spotlight containing a convex lens. A red filter is placed in front of the spotlight. The spotlight is directed at a blue object.

Explain why the blue object appears black.

Visible light is used for communications. Which other parts of the electromagnetic spectrum are used for communications?

Tick (✓) two boxes.

Figure 5 shows a ray of light in an optical fibre.

What is the name given to the dotted line on Figure 5 ?

Where the ray of light touches the edge of the optical fibre it is reflected. Draw the reflected ray on Figure 5.

Optical fibres need to be able to bend around corners without breaking. Suggest the property that optical fibres must have to allow them to bend around corners.

The appearance of visible light can change when it interacts with different objects. Complete the sentences. Choose the answers from the box. Each answer may be used once, more than once or not at all.

When white light is incident on a green filter, only green light passes through the filter.

Some objects are transparent and some objects are opaque.

Which one of the objects in Figure 5 is transparent? Tick one box.

Complete the sentence. Choose an answer from the box.

absorb reflect transmit

A student wears a white T-shirt and a red baseball cap to a party.

Why does the T-shirt look white in white light?

Explain how the colour of the baseball cap appears to change when the room lights at the party change from white to blue.

A student investigated how the type of surface affects the amount of infrared radiation the surface absorbs. Figure 6 shows the equipment that the student used.

The metal sheets absorb infrared radiation. The wax melts and the drawing pins fall off the surfaces.

In the investigation there are several variables. Draw one line from each variable to the correct description of that variable.

Variable Description

What is the main hazard in this investigation?

The drawing pin attached to the matt black metal sheet fell off first. What can be concluded from this result?

Figure 7 shows the apparatus a student used to investigate the reflection of light by a plane mirror. The student drew four ray diagrams for each angle of incidence. The student measured the angle of reflection from each diagram. Table 2 gives the student’s results.

For each angle of incidence, the angle of reflection has a range of values. This is caused by an error. What type of error will have caused each angle of reflection to have a range of values?

Suggest what the student may have done during the investigation to cause each angle of reflection to have a range of values.

Estimate the uncertainty in the angle of reflection when the angle of incidence is 50°. Show how you determine your estimate.

The student concluded that for a plane mirror, the angle of incidence is equal to the angle of reflection. Explain whether you agree with this conclusion. Use examples from the results in Table 2 in your answer.

What extra evidence could be collected to support the student’s conclusion?

State one change the student should make to the apparatus if he wants to use the same method to investigate diffuse reflection.