Electromagnetic spectrum：練習題

Which of the following electromagnetic waves has the longest wavelength?

Which region of the electromagnetic spectrum is used for both cooking food inside specialized ovens and for transmitting signals to and from communication satellites?

Exposure to which type of electromagnetic radiation is associated with the harmful effect of internal heating of body cells, and which type is used primarily for security scanning of luggage at airports?

A list shows different regions of the electromagnetic spectrum: microwaves, visible light, radio waves, and ultraviolet.
Which of these regions is arranged correctly in order of increasing frequency?

A radio wave is travelling through a vacuum with a wavelength of \( 1.5 \times 10^{3} \text{ m} \).
Using the speed of electromagnetic waves as \( 3.0 \times 10^{8} \text{ m/s} \), what is the frequency of this radio wave?

Compare the typical use of ultraviolet radiation (UV) in security marking with the use of infrared radiation (IR) in short-range communications, and state one distinct health hazard associated with excessive exposure to UV radiation.

A signal is transmitted using visible light through an optical fibre and another signal is transmitted through the air using microwaves. If the wavelength of the light is \( 5.0 \times 10^{-7} \text{ m} \) and the frequency of the microwaves is \( 3.0 \times 10^{10} \text{ Hz} \), calculate the ratio of the frequency of the visible light to the frequency of the microwaves. (Assume the speed of electromagnetic waves in both media is approximately \( 3.0 \times 10^8 \text{ m/s} \)).

A specific type of electromagnetic radiation is used for security marking on items and for sterilising water. State the name of this radiation and explain why it is effective for sterilising water.

Ultraviolet (UV) radiation is a specific region of the electromagnetic spectrum with unique properties.

(a) A UV wave has a frequency of \( 8.0 \times 10^{14} \text{ Hz} \). Calculate its wavelength in a vacuum, given that the speed of all electromagnetic waves is \( 3.0 \times 10^8 \text{ m/s} \). (2)
(b) Explain why UV radiation is more hazardous to human skin than visible light, referring to the relationship between frequency and energy. (2)
(c) State one common practical use for ultraviolet radiation in a domestic or industrial setting. (1)

The electromagnetic spectrum consists of waves travelling at the speed of light, but spanning a wide range of frequencies and wavelengths.

(a) State the names of the seven main regions of the electromagnetic spectrum in order of increasing wavelength, starting with the region that has the highest frequency.

(b) A communication system uses microwaves with a frequency of \( 1.5 \text{ GHz} \) (GigaHertz).

(i) Calculate the wavelength of these microwaves in metres. (Assume the speed of electromagnetic waves in air is \( 3.0 \times 10^8 \text{ m/s} \)).

(ii) Suggest two reasons why microwaves are particularly suitable for transmitting signals between mobile phones and satellites.

(c) The Earth's atmosphere is mostly transparent to visible light, which is used for illumination and vision. Explain why visible light of a single frequency is often described as monochromatic.