GCSe Physics - Part 1B

Key points, key words, equations and examiners tips

HideShow resource information
  • Created by: Katy Head
  • Created on: 16-05-11 20:56

The electromagnetic spectrum

Key points:-

  • The electromagnetic spectrum (in order of increasing wavelength): Gamma rays, X-rays, Ultra-violet, visible, infra-red, mocrowaves and radio waves
  • All electromagnetic waves travel through space or a vacuum at a speed of 300 million metres per second
  • Wave speed (metres per second) = frequency (hertz) * wavelength (metres)

Key words:- electomagnetic spectrum, wave speed, wavelength, frequency

Examiners Tips:-

  • Electromagnetic waves transfer energy and not matter
  • Examination questions often come up about the electromagnetic spectrum. Make sure you can put the parts of the spectrum in the correct order
1 of 13

Gamma Rays and X-rays

Key Points :-

  • X-rays and Gamma radiation are absorbed by dense materials in bone and by metal
  • X-rays and Gamma radiation damage living tissue when they pass through it
  • X-rays are used in hospital to take radiographs
  • Gamma Rays  are used to kill harmful bacteria in food, to sterilise surgical equipment and to kill cancer cells

Key words:- Gamma rays, X-rays, dose, cancer

Examiners tips :-

  • Gamma radiation can cause cancer but it is also used to treat cancer

 

2 of 13

Light and Ultraviolet Radiation

Key Points :-

  • Ultraviolet radiation is in the electromagnetic spectrum between visible light and X-rays
  • Ultraviolet radiation has a shorter wavelength than visible light
  • Ultraviolet radiation can harm the skin and the eyes

Key words:- Ultraviolet, fluorescent, visible, optical fibres

Examiners tips:-

  • Make sure you can explain in detail some applications and hazards of Ultraviolet radiation
3 of 13

Infra-red, mocrowaves and radio waves

Key points:-

  • Infra-red: Heaters, communications (remote handsets, optical fibres)
  • microwaves:  Microwave ovens, communications
  • radio waves: communications

Key words:- infra-red radiation, microwaves, radio waves, communications, optical fibres, transmitters.

Examiners tips:-

  • Make sure that you can explain the effects of different wavelengths of electromagnetic radiation on living cells
  • Knowing the detail here is important - it will gain you extra marks
4 of 13

Communications

Key Points :-

  • The use we make of radio waves depends on the frequency  of the waves
  • Visible light  and infra-red radiation are used to carry signals in optical fibres

Key words:- communications, optical fibres, reflections

Examiners tips:-

  • Remember that the radio wave part of the electromagnetic spectrum covers a large range of frequencies; from 3000 million Hz to less than 300,000 Hz.
  • The range of wavelengths is 0.1 metre to more than 1 kilometre
5 of 13

Analogue and Digital signals

Key Points :-

  • Analogue signals vary continuously in amplitude
  • Digital signals are either high (1) or low (0)
  • Digital transmission, when compared with analogue transmission,  is free of noise and distortion. It can also carry much more information.

Key words:- Analogue, Digital, noise, amplitude, amplified, distortion

Examiners tips:-

  • In this context, 'noise' means unwanted, usually random, impulses that get added to the original signal
  • Remember that digital signals can carry much more information than analogue signals
  • Digital pulses can be made very short so that many pulses can be transmitted each second
6 of 13

Observing Nuclear Radiation

Key points:-

  • A radioactive substance contains unstable nucleii
  • An unstable nucleus becomes stable by emitting radiation
  • There are three main types of radiation from radioactive substances
    • Alpha, Beta and Gamma radiation
  • Radioactive decay is a random event - we cannot predict or influence when it will happen

Key words- nucleii, proton, neutron, electron, radioactive decay, alpha particles, beta particles, gamma rays

Examiners tips :-

  • Radioactive decay is a random process - it is not possible to predict when any particular nucleus will decay and it is not possible to make any particular nucleus decay
  • Radioactive decay is not effected by external conditions. You cannot make it happen faster by changing things like temperature or pressure
7 of 13

Alpha, Beta and Gamma Radiation

Key points:-

  • Alpha radiation is stopped by paper or a few centimetres of air
  • Beta radiation is stopped by thin metal or about a metre of air
  • Gamma radiation is stopped by thick lead and has an unlimited range in air

Key words:- ionisation, electric and magnetic fields, charge

Examiners tips:-

  • For each of the three types of radiation you need to remember
    • what it is
    • how ionising it is
    • how far it penetrates different materials
    • if it is deflected by electric and magnetic fields
8 of 13

Half Life

Key points :-

  • The half-life of a radioactive substance is the time it takes:-
    • for the number (and therefore the mass) of parent atoms in a sample to halve
    • For the count rate from the original substance to fall to half its original level

Key words:- half life, count rate

Examiners tips:-

  • Practice doing half-life calculations
9 of 13

Radioactivity at work

Key points:-

  • The use we can make of a radioactive substance depends on :-
    • its half-life
    • the type of radiation it gives out

Key words :-  tracers

Examiners tips :-

  • For each radiation you should know an application why a particular source is used and the approximate half-life
10 of 13

The Exapanding Universe

Key Points:-

  • Light from a distant galaxy is red shifted to longer wavelengths
  • The further away the galaxy the bigger the red shift

Key words:- red shift, galaxies

Examiners tips:-

  • The further away a galaxy is from us the faster it is moving away from us
11 of 13

The Big Bang

Key points:-

  • Red shift provides evidence that the universe is expanding
  • The universe started with the Big Bang, a massive explosion from a very small point

Key words:- expanding, Big Bang

Examiners tips-

  • Be sure you can explain why red shift is evidence for an exanding universe and the Big Bang
12 of 13

Looking into Space

Key points :-

  • Observations are made with telescopes that may detect visible light or other electromagnetic radiations
  • Observations of the Solar System and galaxies can be carred out from the Earth and from Space

Key words:- telescope, atmosphere, satellite

Examiners tips :-

  • Not all telescopes detect visible light, Some 'see' into Space by detecting radiation from other parts of  the electromagnetic spectrum
13 of 13

Comments

No comments have yet been made

Similar Physics resources:

See all Physics resources »See all Electromagnetic Spectrum resources »