Electromagnetic waves

Food colouring can be used to change the colour of water.

A student investigated how the colour of water affects the time taken for the water to cool.

This is the method used.

1. Put 200 cm³ of hot water into a conical flask.

2. Add four drops of food colouring to the water.

3. Place a digital thermometer in the water.

4. Start a timer when the temperature of the water is 80.0 °C.

5. Record the time taken for the water to cool to 65.0 °C.

6. Repeat steps 1 to 5 using different colours of food colouring.

Figure 3 shows the apparatus.

What was the independent variable in this investigation?

Tick () one box.

Which of the following was a control variable in this investigation?

Tick () one box.

What equipment should have been used to make sure 200 cm³ of water was put in the conical flask?

Tick () one box.

The student also tested water with no food colouring.

The temperature of the water changed from 80.0 °C to 65.0 °C in a time of 5.0 minutes.

Calculate the average rate of change of temperature of the water.

Use the equation:

Table 1 shows the results for the different coloured water.

Complete Figure 4.

You should:

• label the y-axis

• add a scale to the y-axis

• draw bars for the green water and the violet water.

In the visible spectrum, orange light is between red light and yellow light.

Estimate the rate of change of temperature if orange food colouring was used.

Use Table 1.

Complete the sentence.

Choose the answer from the box.

The results show that the colour of the water affects the rate at which the

Complete the sentence.

Choose the answer from the box.

The water in each conical flask cools down because the electromagnetic radiation

Some homes are connected to the internet using satellites.

Electromagnetic waves are used to transmit data between Earth and the satellites.

Which electromagnetic waves are used to transfer data between Earth and satellites?

Tick () one box.

Which of the following electromagnetic waves has the greatest frequency?

Tick () one box.

What is meant by the ‘period of a wave’?

Tick () one box.

Data is transmitted to the satellites by electromagnetic waves with a frequency of 48 GHz.

Calculate the period of waves with a frequency of 48 GHz.

Use the Physics Equations Sheet.

Choose the unit from the box.

The satellites receive and transmit data using electromagnetic waves with different frequencies.

Give one property that is the same for electromagnetic waves with different frequencies.

Most homes are connected to the internet using cables.

Suggest one reason why homes in some areas of the UK are connected to the internet by satellites.

A pair of sunglasses has lenses that absorb all ultraviolet and some visible light.

Ultraviolet and visible light are both transverse waves.

What is meant by ‘transverse waves’?

Ultraviolet can cause sunburn and eye damage.

Give one other risk to health from exposure to ultraviolet.

Complete the sentence.

Compared with the wavelength of visible light, the wavelength of ultraviolet

A wave of visible light has a frequency of 6.25 × 10¹⁴ Hz.

Calculate the wavelength of this light.

Use the Physics Equations Sheet.

Give your answer in nanometres (nm).

A ray of visible light incident on the lens in a pair of sunglasses is refracted.

Figure 3 shows a wave front diagram for visible light incident on the lens.

For each wave front, one end of the wave front enters the lens before the other end.

Explain why the light refracts as it enters the lens.

Figure 4 shows a ray of visible light incident on glass.

The angle of incidence is 45°.

The angle of refraction of the ray in the glass is 28°.

Complete the ray diagram in Figure 4 to show the path of the ray in the glass.

You should:

• draw the normal line

• draw the refracted ray in the glass.

You do not need to draw the ray leaving the glass.

A student used a temperature probe to measure the temperature of melting ice.

This is the method used.

1. Place the temperature probe in iced water and record the temperature.

2. Remove the probe from the iced water and allow the probe to return to

room temperature.

3. Repeat steps 1 and 2 four more times.

The measurements were:

–0.5 °C +0.2 °C –0.3 °C +0.5 °C +0.1 °C

What type of error is shown by the measurements?

Determine the uncertainty in the measurements.

The student investigated how the colour of an object affects the rate of change of

temperature of the object.

This is the method used.

1. Make two identical cubes using clay.

2. Paint one cube black and paint one cube white.

3. Push a temperature probe into the centre of each cube.

4. Place the cubes 10 cm from an infrared heater.

5. Record the temperature of each cube every two minutes.

Table 1 shows the results for the white cube.

Complete Figure 7.

You should:

• use a suitable scale for the y-axis

• plot the data from Table 1

• draw a line of best fit.

The data for 10 minutes and 12 minutes have been plotted for you.

The temperature of the black cube increased from 18 °C to 63 °C in the first 2.0 minutes.

Calculate the average rate of change of temperature of the black cube in the first 2.0 minutes.

Give your answer in °C/s.

The student made two observations:

1. The rate of change of temperature was initially greater for the black cube than for the white cube.

2. After a few minutes, both cubes stopped changing temperature.

Explain the student’s observations.

You should refer to the absorption and emission of radiation from the surfaces of the cubes.

Electromagnetic waves are grouped according to their wavelength and frequency.

Electromagnetic waves are transverse waves and can travel through a vacuum.

Give one other property that is the same for all types of electromagnetic wave.

What is meant by ‘transverse wave’?

Which group of electromagnetic waves is used for satellite communications?

Visible light is the only group of electromagnetic waves that the human eye can detect.

Which colour of visible light has the shortest wavelength?

The three highest frequency groups of electromagnetic waves are hazardous.

Describe a risk linked to each group of high frequency electromagnetic wave.

Figure 5 shows a person using a mobile phone to allow a laptop to access

the Internet.

The electromagnetic waves emitted by the mobile phone send information to the laptop.

The electromagnetic waves emitted by the mobile phone have a period

Calculate the frequency of the waves.

Use the Physics Equations Sheet.

Give your answer in standard form.

The electromagnetic waves are produced by oscillations in the transmitter of the mobile phone.

Explain how oscillations in the transmitter enable information to be transferred to the detector in the laptop.

The Sun emits a continuous spectrum of electromagnetic waves. Figure 14 names some of the groups of waves in the electromagnetic spectrum.

Name groups A, B and C in Figure 14.

Give one similarity and one difference between the properties of ultraviolet waves and gamma rays.

Figure 15 shows white light split into a spectrum of different colours by a glass prism.

Light changes direction when it enters the glass prism. What name is given to this process?

Use the Physics Equations Sheet to answer questions 06.4 and 06.5.

Write down the equation that links frequency (f), wavelength (λ) and wave speed (v).

The wave in the middle of the spectrum has a wavelength of 5.0 × 10^–7 m. wave speed of light = 3.0 × 10⁸ m/s Calculate the frequency of the wave.

The Sun emits a continuous spectrum of electromagnetic waves. Figure 1 names some of the groups of waves in the electromagnetic spectrum.

Name groups A, B and C in Figure 1.

Give one similarity and one difference between the properties of ultraviolet waves and gamma rays.

Figure 2 shows white light split into a spectrum of different colours by a glass prism.

Light changes direction when it enters the glass prism. What name is given to this process?

Use the Physics Equations Sheet to answer questions 01.4 and 01.5.

Write down the equation that links frequency (f), wavelength (λ) and wave speed (v).

The wave in the middle of the spectrum has a wavelength of 5.0 × 10^–7 m. wave speed of light = 3.0 × 10⁸ m/s Calculate the frequency of the wave.

There are different types of electromagnetic waves.

What do all electromagnetic waves transfer? Tick (✓) one box.

Complete the sentence. Choose answers from the box.

Different types of electromagnetic waves have a different

Figure 1 shows the electromagnetic spectrum.

Give the names of parts A and B of the electromagnetic spectrum.

Different types of electromagnetic waves have different uses. Draw one line from each type of electromagnetic wave to its use. Type of electromagnetic Use wave

A student investigated how the colour of a surface affects the amount of infrared radiation the surface absorbs. Figure 7 shows the equipment used. The two flasks are painted different colours.

This is the method used.

1. Pour water at 20 °C into each flask.

2. Place a bung and thermometer into each flask.

3. Place each flask in front of the infrared lamp.

4. Measure the temperature of the water every 30 seconds for 10 minutes.

Explain two improvements to the method the student used.

Figure 8 shows the results for each flask.

Complete the sentences.

After 100 seconds the temperature difference between the black flask and the

The temperature of the white flask stopped increasing. The temperature inside the

The initial rate of absorption of infrared radiation by the black flask was greater than the initial rate of absorption by the white flask. How does Figure 8 show this?

Explain why the temperature of the water in the flasks increased and then became constant.

Scientists are developing a rocket aeroplane designed to travel much faster than jet aeroplanes.

The rocket aeroplane must accelerate along a runway to take off.

What would happen to the air resistance acting on the rocket aeroplane as it accelerates?

During the first 14 seconds the average speed of the rocket aeroplane on the runway will be 35 m/s.

Calculate the distance that the rocket aeroplane will travel during the first 14 seconds.

Use the equation:

distance travelled = average speed × time

Write down the equation which links distance (s), force (F) and work done (W).

When the rocket aeroplane travels a distance of 270 m on the runway the engines will do 54 000 000 J of work.

Calculate the average force exerted by the engines.

The rocket aeroplane will fly at a greater height than a jet aeroplane.

The height that an aeroplane flies at affects the radiation dose a passenger will receive each hour.

Table 2 shows the speed of each aeroplane and the radiation dose a passenger will receive each hour.

Exposure to ionising radiation has risks and possible consequences.

Evaluate the risks and possible consequences of flying in a rocket aeroplane and in a jet aeroplane.

Assume the same journey is made in each aeroplane.

Use values from Table 2.

Different parts of the electromagnetic spectrum are used in medical imaging. Figure 8 shows an image of a person’s hand taken with an infrared camera.

Explain why the infrared camera is able to show that parts of the hand are at different temperatures.

Infrared has a range of wavelengths from 700 nm to 1 mm. Which part of the electromagnetic spectrum would have waves with a wavelength of

Tick (✓) one box.

Figure 9 shows X-rays and gamma rays being used for medical imaging.

Figure 9

To use X-rays for medical imaging, a machine produces a very brief burst of X-rays. To use gamma rays for medical imaging, a radioactive isotope is injected into the patient’s blood. The isotope is circulated around the body in the blood. The isotope emits gamma rays.

Compare the potential risks to a patient of using X-rays and gamma rays for medical imaging.

X-rays are produced by colliding high-energy electrons into a metal target. The electrons have high energy because they are accelerated to high speeds. Only a small proportion of the kinetic energy of an electron is converted into an X-ray when it collides with the metal target.

An electron is accelerated through a distance of 15 mm. The work done on the electron is 1.2 × 10^–13 J. Calculate the force on the electron.

The metal target is made from tungsten. Tungsten has the highest melting point of any metal. Explain why using tungsten as the metal target enables the X-ray machine to be more powerful.

X-rays and gamma rays are types of electromagnetic waves. X-rays are used for medical imaging.

Which substance will not absorb X-rays? Tick (✓) one box.

Table 1 shows the effect of exposure to different doses of radiation.

During one X-ray a person receives a dose of 0.100 mSv Why is this dose unlikely to harm the person?

A doctor takes an X-ray photograph of a person. When taking the X-ray photograph, the doctor stands behind a screen. Suggest why.

Which of the following are gamma rays used for? Tick (✓) one box.

Why are gamma rays and X-rays harmful to humans? Tick (✓) one box.

Electromagnetic waves are also used in communications. Describe how microwaves and visible light are used in communications.

X-rays form part of the electromagnetic spectrum. Radiographers use X-rays to produce images of bones inside the body.

Explain why X-rays can be used to produce images of the bones inside the body.

Table 2 shows the effect of exposure to different doses of radiation.

During an X-ray a person receives a dose of 0.5 mSv The radiographer takes many X-ray images each day. Explain why the radiographer stands behind a protective screen when taking an X-ray image.

Radio waves form part of the electromagnetic spectrum. Figure 10 shows one use of radio waves.

Explain how electrical signals in the transmitter produce a signal in the receiver.

The Sun emits all types of electromagnetic waves.

Figure 7 shows the electromagnetic spectrum.

Complete the sentences.

Choose answers from the box.

Explain why it is important that the Earth’s atmosphere absorbs gamma rays emitted by the Sun.

Some microwaves are not absorbed by the Earth’s atmosphere.

Why is this useful?

Some ultraviolet (UV) radiation from the Sun passes through the atmosphere and reaches the surface of the Earth.

The amount of UV radiation that reaches the surface of the Earth can be measured on a scale called the UV index.

Figure 8 shows the average midday UV index in the UK for 1 year.

Why is exposure to UV radiation harmful to humans?

Compare the risk from UV radiation at different times of year in the UK.

Use data from Figure 8.

Wave front diagrams are used to explain why light refracts when it passes from air into glass.

Explain why the light refracts as it passes from air into glass.

Figure 11 shows a ray of red light entering a glass prism.

Complete the ray diagram to show the ray emerging from the glass prism.

White light is made up of a continuous spectrum of different wavelengths that all travel

Rainbows are produced because different wavelengths of light travel at different speeds in water.

Figure 12 shows the speed of different wavelengths of light in water.

Explain why violet light is refracted the most as it enters water.

Figure 5 shows types of waves within the electromagnetic spectrum.

Some of the types of waves are represented by letters.

Which letter shows the position of ultraviolet (UV) radiation within the electromagnetic spectrum?

Tick one box.

A special lamp can produce UV radiation.

Which two statements describe the electromagnetic waves emitted by a UV lamp?

Tick two boxes.

UV radiation is used to treat a vitamin D deficiency.

People should not use a UV lamp for long periods of time.

State two risks of exposure to high levels of UV radiation.

Ionising radiation is used for some medical imaging.

Name two types of electromagnetic waves that are used.

A car aerial receives radio waves from a radio transmitter. Radio waves are transverse waves. Sound waves are longitudinal waves.

Describe the difference between transverse waves and longitudinal waves.

The radio waves have a frequency of 4.8 × 10⁹ Hz Wave speed of electromagnetic waves = 3.0 × 10⁸ m/s Calculate the wavelength of the radio waves. Give your answer to 2 significant figures.

Describe how the radio waves reaching the car aerial produce signals in the electrical circuit of the car radio.