Electromagnetic Spectrum

Question 1

4 properties of electromagnetic waves

Answer 1

1. All electromagnetic waves are transverse waves that travel with the same speed in vacuum
2. The speed of all electromagnetic waves in vacuum is 3 x 10^8 m s-1 in vacuum.
3. The frequency of electromagnetic waves ranges from nearly 0Hz to 10^20Hz
4. The wavelength of the waves can be calculated with the formula v = f入

Question 2

7 main components of the electromagnetic spectrum

Answer 2

Radiowaves, microwaves, infrared, visible light, ultraviolet radiation, X-rays and gamma rays

Question 3

How are radiowaves produced

Answer 3

They are produced from an AC in a tuned electrical circuit

Question 4

Properties of radiowaves

Answer 4

They have long wavelengths and low frequencies.

Question 5

Uses of radiowaves

Answer 5

• Radio and television communication
• Radiowaves of higher frequencies are used for rapid transfer of information in satellite TV because they can carry more information per unit time than radio waves of lower frequencies
• Radiowaves of lower frequencies are used in traditional radio stations.

Question 6

How are microwaves produced

Answer 6

Microwaves are produced by oscillations of electrons in a vacuum.

Question 7

Uses of microwaves

Answer 7

• Microwaves of 2450Hz are used in microwave ovens for cooking because it allows water molecules that have a natural frequency of 2450Hz to resonate with it. The water molecules then gain kinetic energy and increase in temperature to cook the food.
• Microwaves are also used to transfer data for satellite TV broadcasts and short-range internet links.

Question 8

How is infrared produced

Answer 8

Infrared is radiation given out at a frequency of about 10^13 Hz, such as from bodies at room temperature.

Question 9

Uses of infrared

Answer 9

• Television controls and intruder alarms
• Night vision binoculars to indicate the presence of warm objects when visible light is absent.

Question 10

Range of frequencies of visible light

Answer 10

• violet: 380 - 450nm
• blue: 450 - 495nm
• green: 495 - 570nm
• yellow: 570 - 590nm
• orange: 590 - 620nm
• red: 620 - 750nm

Question 11

Uses of visible light

Answer 11

• optical fibres for medical uses
• telecommunications

Question 12

How is ultraviolet radiation produced

Answer 12

Ultraviolet radiation is produced by high energy electron transmissions

Question 13

What is emitted from ultraviolet radiation

Answer 13

Ultraviolet light causes the emission of visible light from certain substances.

Question 14

Uses of ultraviolet radiation

Answer 14

• sunbeds
• sterilisation in hospitals and science labs

Question 15

How are x-rays produced

Answer 15

X-rays are produced from the collision of high energy electrons with a metal target

Question 16

Properties of x-rays

Answer 16

X-rays have very high frequency, allowing it to pass through matter and affect photographic film

Question 17

Uses of x-rays

Answer 17

• radiological and engineering applications, such as to reveal the insides of an object photographed with x rays

Question 18

How are gamma rays emitted

Answer 18

Gamma rays are emitted when a nucleus loses energy after a nuclear reaction

Question 19

Properties of gamma rays

Answer 19

Gamma radiation have frequency in the region of 10^20 Hz and energies in the order of the megaelectronvolt. Gamma radiation is even more penetrating than x-rays.

Question 20

Uses of gamma rays

Answer 20

• medical treatment

Question 21

Effects of absorbing radiowaves/microwaves

Answer 21

• causes slight heating when absorbed by the body but do not change the structures of the cells
• strong sources of radio signals could interfere with electronic devices such as pacemakers to malfunction

Question 22

Effects of absorbing infrared radiation

Answer 22

• causes burns, only low levels of infrared radiation cause no harm

Question 23

Effects of absorbing visible light (of high power)

Answer 23

Visible light with high power such as lasers can damage the eyes and burn the skin

Question 24

Effects of absorbing ultraviolet radiation

Answer 24

• triggers the release of chemicals in the skin that causes redness and swelling that looks similar to a burn.
• can change the structure of the skin’s DNA and lead to skin cancer

Question 25

Effects of absorbing x rays/gamma rays

Answer 25

• they possess enough energy to remove electrons from atoms in a process called ionization
• ionization of atoms part of a living cell can affect the ability of the cell to carry out its function or even rupture the cell wall.
• if a large number of cells which are part of a vital organ become affected, the organism could die
• therefore, exposure to x rays and gamma rays is limited.