Topic 5 : Light and the EM spectrum

Question 1

Virtual Image:

Answer 1

An image produced by the apparent, but not actual, divergence of light-rays. Virtual images cannot be projected onto a screen.

Question 2

Visible light

Answer 2

Visible Light: The only type of electromagnetic radiation that our eyes can detect.
It is used for fibre optic communications and photography.

Question 3

X-rays

Answer 3

X-Rays: Used for medical imaging and security scanners. They can cause cell damage and mutations.

Question 4

Ultraviolet

Answer 4

Ultraviolet: Used in energy efficient lamps, disinfecting water, and for sun tanning. It can cause cell and eye damage that can result in skin cancer and eye conditions.

Question 5

Gamma rays

Answer 5

Gamma Rays: High energy radiation rays used for detecting and treating cancers, and sterilising food and medical implements. They can cause cell damage and mutations.

Question 6

Infrared radiation

Answer 6

Infrared Radiation: A type of radiation that all objects emit and absorb. The hotter an object is, the greater the infrared radiation it emits in a given time.

Question 7

Em spectrum

Answer 7

Electromagnetic Spectrum: A group of transverse waves that cover a large range of frequencies and wavelengths. The highest frequency waves in the spectrum are gamma-rays and the lowest are radio waves.

Question 8

Electromagnetic Waves: Transverse waves that transfer energy from the source of the waves, to an absorber. They form a continuous spectrum of different frequencies and all travel at the same speed in a vacuum.

Answer 8

Electromagnetic wave s

Question 9

Danger of the EM spectrum

Answer 9

Higher frequency EM waves have more energy, so exposure can transfer too much energy to cells, causing them to mutate and potentially damage them/causing cancer
Microwaves
-
Internal heating of body cells
Infra-Red
Skin burns
Damage to surface cells and eyes, leading to skin cancer
X-ray/Gamma -
Mutation or damage to cells in the body
Uses of the EM spectrum,
- Radio
-
- Microwave
- IR
- Visible
- UV
- X-ray
- Gamma
Communications, satellite transmission.
• They can be produced by oscillations in electrical circuits, or they can induce oscillations in electrical circuits
Cooking, communication
Cooking, thermal imaging, short range communication, optical fibres
Vision, photography, illumination
Security marking, fluorescent lamps, disinfecting water
Observing internal structure of objects, airport/medical scanners Sterilising food/medical equipment, treating cancer