Radiation and the Universe

Physics P1b 

 

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Question

What are waves?

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Answer

Waves are vibrations that transfer energy from place to place without matter (solid, liquid or gas) being transferred.

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Question

What do some waves travel through?

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Answer

Solid, liquid or gas

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Question

What is a seismic wave?

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Answer

Vibrations caused by the earth

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Question

What do other waves travel through?

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Answer

Empty space

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Question

What is amplitude?

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Answer

The volume of a wave

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Question

What is frequency and what is it measured in?

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Answer

The amount of waves per second.

Hertz (Hz)

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Question

How fast do waves travel?

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Answer

wave speed (metre per second) = frequency (Hz) x wavelength (metres)

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Question

What is the visible spectrum?

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Answer

When light is refracted the shorter the wavelength of the light, the more it is refracted. As a result, red light is refracted the least and violet light is refracted the most, causing the coloured light to spread out to form a spectrum

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Question

What is the electromagnetic spectrum?

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Answer

Visible light is just one type of electromagnetic radiation. There are various types of electromagnetic radiation, some with longer wavelengths than visible light and some with shorter wavelengths than visible light.

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Question

What are the different types of waves?

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Answer

 Gamma       highest

X-ray

Ultraviolet

Visible light

Infra Red

Micro-waves

Radio-waves    lowest 

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Question

What are their uses?

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 Gamma     -  killing cancer cells

X-ray          - medical images of bones

Ultraviolet  - detecting forged bank notes by fluoresence

Visible light - seeing

Infra Red   - optical fibre communication

Micro-waves - cooking

Radio-wave - television signals

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Question

What are scientists main theory on the how the universe began?

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Answer

Scienctists main theory is the Big Bang. The theory states that originally all the matter in the universe was concentrated into a single incredibly tiny point. This began to enlarge rapidly in a hot explosion, and it is still expanding today.

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Question

How long ago was the big bang?

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Answer

13.6 billion years ago

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Question

What is the Doppler effect?

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Answer

where there is a change in frequency and wavelength

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Question

What do atoms contain?

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Answer

Three sub atomic particles

protons, neutrons and electrons

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Question

Where are the protons electrons and neutrons found?

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Answer

The protons and neutrons are found in the nucleus of the atom and the electrons are arranged in energy levels or shells around the nucleus

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Question

What are isotopes?

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Answer

Atoms that have different numbers of neutrons in the nucleus

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Question

What is an Alpha particle?

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Answer

  • it is a helium nucleus
  • it is made up of 2 protons and 2 electrons
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Question

What is a beta particle?

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Answer

  • a high speed electron from the nucleus
  • it is emitted when a neutron changes to an electron and proton (the proton remains in the nucleus) 
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Question

What is gamma radiation?

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Answer

  • a very short wavelength electromagnetic radiation that is emitted from the nucleus
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Question

How penetrating are these radioactive substances

  • Alpha
  • Beta 
  • Gamma
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Answer

  • Alpha - not penetrating. can be stopped by a thin piece of paper, human skin or even a few centimeters of air
  • Beta  - they penetrate further than alpha and will be blocked by a few meters of air or a thin sheet of aluminum
  • Gamma - very penetrating. several centimeters of lead and several meters of concrete are needed to block it.
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Question

What is half life?

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Answer

The time it takes

  • for the number (and also mass) of parent atoms in a sample to halve 
  • for the count rate from the original substance to fall to half its initial level
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