IGCSE Physics EM spectrum topical questions

Name the region of the electromagnetic spectrum used for each purpose.

1. (a)Cooking food quickly in an oven[1]
2. (b)Seeing a broken bone inside an arm[1]
3. (c)A television remote controller[1]

Arrange the five regions microwaves, gamma rays, radio waves, visible light and ultraviolet in order, and answer about the family.

1. (a)Arrange the regions in order of increasing frequency.[2]
2. (b)State the speed at which all these waves travel in a vacuum.[1]
3. (c)State whether electromagnetic waves are transverse or longitudinal.[1]

A hospital uses several parts of the spectrum every day. Match the safety advice to the region.

1. (a)Radiographers stand behind lead screens when using X-rays. State the harm X-rays can cause.[1]
2. (b)State one harm caused by excessive ultraviolet exposure.[1]
3. (c)State one way a worker can reduce their exposure to any harmful radiation.[1]

A mineral collector checks specimens under an ultraviolet lamp, and a security camera switches to infrared at night.

1. (a)State which region makes the mineral fluoresce.[1]
2. (b)State which region the infrared camera detects.[1]
3. (c)State which of the two regions has the higher frequency.[1]
4. (d)Both are electromagnetic waves. Write down their common speed in a vacuum, with its unit.[1]

A Wi-Fi router transmits microwaves at a frequency of 2.4 GHz (2.4 × 10⁹ Hz).

1. (a)Calculate the wavelength of these microwaves. Take the speed as 3.0 × 10⁸ m/s.[2]
2. (b)State two reasons why microwaves suit mobile communication.[2]

An optician’s shop uses ultraviolet lamps to check bank notes, and an X-ray machine is installed next door at the medical clinic.

1. (a)Describe how the ultraviolet lamp exposes a forged note.[2]
2. (b)Explain why the X-ray room’s walls are lined with lead.[2]
3. (c)Name one use of ultraviolet other than checking bank notes.[1]

A household uses a microwave oven, a TV remote, and a broadband connection delivered through an optical fibre.

1. (a)Name the region of the spectrum inside the microwave oven, and state what it does to the food.[2]
2. (b)Name the region used by the remote controller.[1]
3. (c)State which waves travel along the optical fibre, and name the effect that keeps them inside the glass.[2]

A digital radio station broadcasts radio waves at a frequency of 220 MHz (2.2 × 10⁸ Hz). A satellite link uses microwaves at 12 GHz (1.2 × 10¹⁰ Hz). Take v = 3.0 × 10⁸ m/s.

1. (a)Calculate the wavelength of the radio broadcast, to 2 significant figures.[2]
2. (b)Calculate the wavelength of the satellite microwaves.[2]
3. (c)State which signal has the shorter wavelength, without further calculation.[1]

A beauty salon offers sessions on a sunbed, which emits ultraviolet radiation.

1. (a)State two harms of excessive ultraviolet exposure.[2]
2. (b)State two precautions the salon could take to reduce the risk.[2]
3. (c)Ultraviolet damage is described as “surface” damage. Suggest why, compared with X-ray damage.[1]

A music fan owns both an old FM radio (which receives analogue radio broadcasts) and a digital radio receiver (which receives digitally encoded broadcasts). The fan drives out of the city into a hilly area.

1. (a)State the difference between an analogue and a digital signal.[2]
2. (b)Explain why the digital receiver keeps producing clear sound further from the transmitter than the analogue one.[3]
3. (c)State one further advantage of digital signalling.[1]

A satellite television company and a satellite phone network both use microwaves. The TV company uses a geostationary satellite; the phone network uses low orbit satellites.

1. (a)Explain what geostationary means, and why it suits fixed TV dishes.[2]
2. (b)Suggest why a phone network might prefer several low orbit satellites even though each one moves across the sky.[2]
3. (c)State the region of the spectrum used in both systems, and give one hazard of excessive exposure to this region.[3]

An undersea fibre-optic cable 4000 km long carries a digital telephone signal. Regenerator units are placed every 50 km along the cable, and each unit rebuilds the pulses to their original clean shape.

1. (a)Describe the difference between the digital pulses in the fibre and the analogue voltage that originally came from the microphone.[2]
2. (b)Explain why the signal is still clear after 4000 km.[2]
3. (c)Calculate how many regenerator units the cable needs.[2]