Waves

• Absorption: Black objects absorb all frequencies of light while white objects reflect.
• Convection is the transfer of heat through the movement of heated and cooled particles, which move due to density changes and heat transfer is faster in liquids and gases due to the mobility of particles.
• Conduction is the transfer of heat through the vibrations of adjacent particles in a material, due to the difference in temperature and heat transfer is slower in solids due to the closeness of particles.
• A conductor is a substance that allows the transfer of heat, such as metals.
• An insulator is a substance that resists the transfer of heat, such as rubber.
• A wave is a disturbance that travels through a substance, and waves transfer energy not matter.
• Mechanical waves require a medium to move through, such as sound waves.
• Electromagnetic waves can travel through a vacuum.
• The medium is the substance that a wave passes through.
• Wavelength is the distance between two identical positions on a wave, such as one crest and the next.
• Amplitude is the maximum distance of movement of a particle from its rest position as a wave passes by.
• Crest is the highest point on a wave.
• Trough is the lowest point on a wave.
• Frequency is the number of waves that pass a fixed point every second measured in Hertz (Hz).
• Period is the time taken for one wave to pass a fixed point - measured in seconds.
• Transverse motion of the medium is perpendicular to the direction of the propagation, such as ocean surface waves, EM waves.
• Longitudinal motion of the medium is parallel to the direction of propagation, particles move backwards and forwards between compressions as the wave is transmitted through the medium, such as sound waves.
• Longitudinal waves show areas of compression and rarefaction, compressions are regions of high pressure due to particles being close together, rarefactions are regions of low pressure due to particles being spread further apart.
• Velocity is the speed of the travel of a wave, calculated as frequency x wavelength.
• Sound wave transmission relies on particles vibrating in different materials, sounds travel very quickly though most solids, sound travels faster through denser solids, such as metals, than through less dense solids, such as rubber, sound travels more slowly in liquids, dolphins use sound waves in water to navigate, and submarines use their sonar systems in a similar way, gas particles are very spread out, so sound waves travel the slowest through gases, such as air.
• Reflection is when lights bounces off the medium.
• Translucent is a material that allows some light to pass through.
• EM waves travel at the speed of light (3 x 10^8 m/s).
• Transparent is a material that allows light to pass through.
• Radio waves are used in television and radio.
• Vibrations take longer to be passed from particle to particle.
• Infrared is used in electrical heaters, short-range communications (tv remote), and thermal imaging cameras.
• Convex lenses make light rays meet at a point (converge).
• When light passes from a less dense to a more dense substance, it is refracted (or bent inwards) towards the normal.
• In order of increasing energy, electromagnetic waves include radio waves, microwaves, infrared waves, visible light waves, ultraviolet (UV) waves, X-rays and gamma rays.
• X-rays kill cancer cells and are used in medical imaging.
• Electromagnetic waves are transverse waves made up of moving magnetic fields and electric fields travelling together.
• Concave lenses make light rays spread out (diverge).
• Gamma rays are used for sterilising medical equipment, radiation therapy for treatment of cancer, and CT scans.
• Refraction is the bending of beams of light as they pass through one medium to another.
• The range of all the different types of electromagnetic radiation is called the electromagnetic spectrum.
• Visible light is a combination of the visible light spectrum: ROYGBIV.
• Visible light is used for viewing colours.
• Opaque is a material that doesn't allow any light to pass through.
• The law of reflection states that the angle of incidence equals the angle of reflection.