Sec 4 Physics Electromagnetic Spectrum topical questions

List the seven regions of the electromagnetic spectrum in order of increasing frequency.

State three properties shared by all electromagnetic waves.

Match each use to its region: killing cancer cells; TV remote controller; mobile phone communication; seeing.

A Wi-Fi router transmits at 2.4 GHz.

1. (a)Convert 2.4 GHz to hertz.[1]
2. (b)Calculate the wavelength of the waves.[2]
3. (c)The router is moved further from a laptop and the signal weakens. State the effect on the received amplitude and on the received frequency.[2]
4. (d)Name the part of the EM spectrum these waves belong to.[1]

A red laser pointer emits light of wavelength 670 nm (6.7 × 10⁻⁷ m).

1. (a)Calculate the frequency of the light.[3]
2. (b)State the region of the EM spectrum just beyond the red end of visible light, and name one use of it.[2]
3. (c)State how the wavelength of ultraviolet compares with 670 nm.[1]

Explain one use and one hazard of ultraviolet radiation.

1. (a)Describe one use of UV and the property that makes it work.[2]
2. (b)Describe the hazard of over-exposure and one protection method.[3]

A radio astronomy dish receives waves of wavelength 21 cm from a hydrogen cloud in space.

1. (a)Name the region of the EM spectrum these waves belong to.[1]
2. (b)Calculate their frequency.[2]
3. (c)Explain one advantage of placing the dish in space or on a remote mountain rather than in a city.[3]

X-ray imaging of a broken arm produces a picture where bones appear bright and flesh appears dark.

1. (a)Explain why the bones appear bright on the image.[2]
2. (b)Explain one reason X-ray doses are kept as low as possible.[2]
3. (c)A lead apron is placed over the patient’s lower body. Explain how it protects those tissues.[2]
4. (d)State why a radiographer leaves the room during the exposure.[1]

Microwave ovens use waves of frequency 2.45 GHz and the oven door contains a metal mesh with holes of about 1–2 mm.

1. (a)Calculate the wavelength of the microwaves.[2]
2. (b)Explain why the mesh keeps the microwaves inside but lets you see the food.[3]
3. (c)State the hazard of microwaves to living tissue and explain why the mesh matters for safety.[3]

The ozone layer in the upper atmosphere absorbs most of the Sun’s ultraviolet radiation before it reaches the ground.

1. (a)Explain why a thinning ozone layer increases the risk of skin cancer.[3]
2. (b)Explain why sunglasses labelled "UV blocking" protect the eyes even if they look dark.[2]
3. (c)State why the danger of UV exposure is greater at midday and near the equator.[2]
4. (d)Name one everyday material that absorbs UV well.[1]

A ground station communicates with a satellite using microwaves of wavelength 7.5 cm.

1. (a)Calculate the frequency of the transmission.[2]
2. (b)Explain why microwaves, and not radio waves of kilometre wavelength, are used for this link.[3]
3. (c)The satellite relays the signal to another continent. Explain why the microwave band suits satellite links generally (two reasons).[3]

A dentist’s X-ray machine produces a narrow beam toward the patient’s jaw. The patient wears a lead apron; the dentist steps away and presses the exposure button on a cable.

1. (a)Explain how the X-ray image of a filled tooth differs from that of an unfilled one.[2]
2. (b)Explain the purpose of the lead apron and of stepping away.[3]
3. (c)X-ray dose is cumulative over a lifetime. Explain what this means for a patient who needs many images.[3]