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# Physics resources for IGCSE or GCSE students

[Science home]

Revision sheets for IGCSE or GCSE physics. This series revision sheets are based on the IGCSE & GCSE syllabuses. Lots of formulas, definitions and key points to learn off. There are also accompanying test sheets to check your memorisation.

The idea is read the information and than print the quiz sheet and try the questions.

Revision Exercise four:

### Waves - Light and Sound

#### Properties of waves

longitudinal waves à move in the same direction as the medium movement

longitudinal waves à move in the same direction as the medium movement transverse waves à move at right angles to the medium movement amplitudeà hight from top to bottom, unit: metre (m)

frequencyà how many pass each second, unit: hertz (Hz)

wavelength à length from start to end of wave, unit: metre (m) period à time taken for wave to pass = 1/frequency

waves transfer energy and information without transferring matter wave speed = frequency × wavelength v = f × λ

frequency = 1/ time period f = 1/ T

waves can be diffracted (spread out) through gaps or when they pass an edge, and the extent of diffraction depends on the wavelength and the physical dimension of the gap

The electromagnetic spectrum

electromagnetic spectrum goes from longest wavelength -- radio, microwave, infra-red, visible, ultraviolet, X-ray and gamma rays – shortest wavelength

electromagnetic waves travel at the same speed in free space

uses of electromagnetic radiations,

• radio waves: broadcasting and communications
• microwaves: cooking and satellite transmissions
• infra-red: heaters and night vision equipment
• visible light: optical fibres and photography
• ultraviolet: fluorescent lamps
• X-rays: observing the internal structure of objects and materials and medical applications
• gamma rays: sterilising food and medical equipment

Detrimental effects of excessive exposure of the human body to electromagnetic waves

• microwaves : internal heating of body tissue
• infra-red : skin burns
• ultraviolet : damage to surface cells and blindness
• gamma rays : cancer, mutation

### Light

light waves are transverse waves which can be reflected, refracted and diffracted the angle of incidence equals the angle of reflection refractive index n=sin i/sin r total internal reflection is used in transmitting information along optical fibres when the angle of incidence is greater than the critical angle c there is total internal reflection the relationship between critical angle c and refractive index N is sin c = 1/N

### Sound

sound waves are longitudinal waves which can be reflected, refracted and diffracted the frequency range for human hearing is 20 Hz – 20 000 Hz an oscilloscope and microphone can be used to display a sound wave by converting it to an electrical signal the pitch of a sound depends on the frequency of vibration the loudness of a sound depends on the amplitude of vibration

Quiz for revision exercise four: Waves - light and sound quiz

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