Uses & hazards of electromagnetic waves

Radio waves and gamma rays both transfer energy.

Give three other similarities between radio waves and gamma rays.

Both radio waves and gamma rays are used in medicine.

Give one medical use of gamma rays.

Explain why exposure to gamma rays can be harmful but exposure to radio waves is not harmful.

Some medical scanners produce radio waves at a specific frequency.

Explain how radio waves are produced at a specific frequency.

Electromagnetic waves are transverse. Figure 13 represents a transverse wave.

Which of the following gives the wavelength of the transverse wave? Tick (✓) one box.

Which of the following gives the amplitude of the transverse wave? Tick (✓) one box.

Microwaves are electromagnetic waves used for mobile phone communications. Which other type of electromagnetic wave is also used for communications? Tick (✓) one box.

Microwaves from a mobile phone take 0.000 009 s to reach a mobile phone mast. speed of microwaves = 300 000 000 m/s Calculate the distance between the mobile phone and the mobile phone mast. Use the equation: distance = speed × time

Mobile phone communications is only one of the uses for microwaves. Give one other use of microwaves.

Ultraviolet is a type of electromagnetic wave.

Give one use of ultraviolet.

An ultraviolet wave has a wavelength of 300 nanometres. Which of the following is equal to 300 nanometres? Tick (✓) one box.

The speed of ultraviolet waves is 3 × 10⁸ m/s. Calculate the frequency of the ultraviolet wave. Use your answer to Question 05.2

Table 1 gives the wavelength of an ultraviolet wave and three other electromagnetic waves.

Draw one line from each wave to the name of the wave.

Electromagnetic waves are transverse. Some other types of wave are longitudinal.

Describe the difference between transverse and longitudinal waves.

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.

Figure 11 shows the position of three types of wave in the electromagnetic spectrum.

Which letter represents infrared in the electromagnetic spectrum?

Tick (✓) one box.

What is infrared used for? Tick (✓) one box.

An infrared camera produces a colour image. Different colours show different temperatures. People emit infrared radiation. Figure 12 shows how the colour of the image of a person on an infrared camera depends on the person’s body temperature.

Complete the sentence. Choose the answer from the box.

The image produced by an infrared camera of a person with a body temperature of

Rescue workers use infrared cameras to search for people trapped under rubble after an earthquake. How does the image of a trapped person change if the person’s body temperature drops from 37 °C to 33 °C?

A student investigated how the type of surface affects the amount of infrared the surface radiates. Figure 13 shows the equipment used.

Complete the sentence. Choose the answer from the box.

Describe how the equipment shown in Figure 13 would be used to compare the infrared radiation emitted from the vertical surfaces of the cube.

Table 1 shows the results.

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

The bar chart in Figure 14 shows two of the results.

Complete the bar chart to show all of the results.

Give one conclusion that can be made from the results.

Figure 12 shows the electromagnetic spectrum.

Which statement is correct for the direction of the arrow in Figure 12 ? Tick (✓) one box.

Explain how the properties of X-rays make them suitable for the medical imaging of bones.

A student investigated the infrared radiation emitted from the sides of a hollow metal cube. The sides of the cube are different colours or textures. Figure 13 shows the equipment used.

Boiling water was poured into the cube. The amount of infrared radiation emitted from each vertical surface was then measured.

Boiling water is a hazard in this investigation. Suggest how the risk of harm could be reduced in this investigation.

What is the control variable in this investigation?

Table 2 shows the results.

The four temperature values in Table 2 cannot be used to show that the infrared detector gives precise readings. Give the reason why.

The student looked at the data in Table 2 and concluded: ‘A black surface always emits more infrared radiation than a white surface.’ Explain how using an infrared detector with a resolution of 1 °C would have affected the student’s conclusion.

Albedo is a measure of the amount of solar radiation reflected by an object compared to the total solar radiation incident on the object. A perfect reflector has an Albedo value of 1.0 A perfect absorber has an Albedo value of 0.0

What is the Albedo value of a perfect black body?

Figure 14 shows two points, A and B, just above the Earth’s surface.

The average Albedo value of the Earth’s surface is 0.3 The Albedo value of thick cloud varies between 0.6 and 0.9 At night the air at point A cools faster than the air at point B. Explain why.