Radiation - The EM Spectrum

Question 1

What is the electromagnetic (EM) spectrum? (2)

Answer 1

The entire range of light that exists. When objects absorb radiation, energy is transferred to their stores.

2. EM waves are transverse waves.

Question 2

Name all 7 parts of the EM spectrum from shortest to longest wavelength.

Answer 2

1. Gamma rays
2. X-rays
3. Ultraviolet
4. Visible light
5. Infrared
6. Microwaves
7. Radio waves

Question 3

What three properties vary as you go from gamma rays to radio waves?

Answer 3

Increasing wavelength

Decreasing energy and frequency - the energy of a photon is directly proportional to is frequency

Question 4

State the speed at which the waves travel in a vaccum.

Answer 4

3 x 10⁸m/s (the speed of light)

Question 5

Describe how electromagnetic waves travel. (3)

Answer 5

1. Waves/rays are emitted from a source.
2. These waves are then transmitted through the air, as the radiation travels in all directions.
3. Some of these waves are reflected, absorbed by an absorber or bounced off - different parts of the EM spectrum react differently to different objects.

Question 6

Describe the features of gamma rays. (4)

Answer 6

1. Emitted from the radioactive decay of unstable atoms
2. Used for medical imaging, cancer treatment and sterilizing
3. The most ionizing - can damage all tissue
4. Highest energy and frequency, shortest wavelength.

Question 7

Describe the features of x-rays. (3)

Answer 7

1. Emitted when electrons drop down energy levels after being excited.
2. Used for medical imaging
3. Ionising - skin cells + soft tissue e.g internal organs

Question 8

Describe the features of ultraviolet radiation. (3)

Answer 8

1. Emitted when electrons drop down energy levels after being excited.
2. Used for killing bacteria and tanning, causes fluorescence.
3. Ionizing - causes skin cancer and eye damage

Question 9

Describe the features of visible light. (3)

Answer 9

1. Emitted when electrons drop down energy levels after being excited
2. Only type of radiation visible to the human eye
3. Longest to shortest wavelengths - ROYGBIV

Question 10

Describe the features of infrared radiation. (2)

Answer 10

1. Emitted from bonds between vibrating atoms

2. Used for heating, carrying TV remote signals

Question 11

Describe the features of microwaves. (2)

Answer 11

1. Emitted from oscillating electrons.

2. Used for heating (excites the molecules in food) and communication

Question 12

Describe the features of radio waves. (3)

Answer 12

1. Produced by oscillations of charged particles - When absorbed by a conductor, they induce an alternating current.
2. Used for communications
3. Lowest energy and frequency, longest wavelength - no associated risks.

Question 13

What types of EM radiation are ionising? What does this mean? (3)

Answer 13

1. Gamma rays, X-rays, ultraviolet.
2. Very short wavelength, high frequency and energy radiation is ionizing - a single photon has enough energy to remove electrons from atoms/molecules, which could cause the cell to become cancerous, unwanted genetic mutations and chemical reactions b/c the behaviour of the cell will change.
3. High amounts of exposure to ionizing radiation can cause cell damage and possible cell destruction.

Question 14

What 3 things can happen when EM radiation is absorbed.

Answer 14

1. Heating
2. Ionization
3. Fluorescence

Question 15

Explain the process of electron excitation.

Answer 15

1. Electron in a low energy level absorbs enough EM radiation, it rises to a higher energy level
2. When the excited electron falls back to its original energy level, energy is lost as electromagnetic radiation - different amounts of energy released causes the emission of different electromagnetic waves.