Physics P1 (Waves)

Waves are vibrations that transfer energy from one place to another. Some types of waves (for example, seismic waves and sound waves) must travel through a substance such as a solid, liquid or gas.They must travel through a medium, and it is the medium that vibrates as the waves travel through.Sounds in the normal range of human hearing is between about 20 Hz and 20 kHz, but the range becomes less as we get older. Sounds with frequencies above about 20 kHz are called ultrasound.

Electromagnetic waves:

• Radio Waves.
• Micro Waves.
• Infrared Rays.
• Visible Light.
• Ultraviolet.
• X rays.
• Gamma Rays.

The electromagnetic spectrum is a continuous range of wavelengths. The types of radiation that occur in different parts of the spectrum have different uses and dangers, which depend on their wavelength and frequency.White light can be split up using a prism to form a spectrum. The light waves are refracted as they enter and leave the prism. 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.

The main types of electromagnetic radiation

energyfrequencywavelengthtype of electromagnetic radiationtypical use lowest lowest longest radio waves television signals microwaves cooking, mobile phones infrared optical fibre communication visible light seeing ultraviolet detecting forged bank notes X-rays medical images of bones highest highest shortest gamma radiation killing cancer cells

The wavelengths vary across the electromagnetic spectrum from about 10–15 m to more than 104 m.

Other waves do not need to travel through a substance. They may be able to travel through a medium, but they do not have to. Visible light, infrared rays, microwaves and other types of electromagnetic radiation are like this. They can travel through empty space.

In transverse waves, the oscilations (vibrations) are parallel to the direction of wave propagation.Light and other types of electromagnetic radiation are transverse waves. All types of electromagnetic waves travel at the same speed through a vacuum.

In longitudinal waves, the particle displacement is perpendicular to the direction of wave propagation. Sound waves and waves in a stretched spring are longitudinal waves.Longitudinal waves show area of compression and rarefaction.

The amplitude of a wave is its maximum disturbance from its undisturbed position.

The wavelength of a wave is the distance between a point on one wave and the same point on…