Electromagnetic waves

• Dark paint absorbs light.
• Every colour has its own narrow band of wavelength and frequency.
• Specular reflection is the reflection from a smooth surface in a single direction.
• Diffuse reflection is the reflection from a rough surface.
• Opaque objects do not allow light to pass through them.
• White objects reflect all wavelengths of light.
• Black objects absorb all wavelengths of light.
• Blue objects only reflect blue light and absorb all other colours.
• A filter only allows a small range of wavelengths to pass through it.
• All objects emit and absorb infrared radiation, regardless of temperature.
• A perfect black body absorbs all radiation incident on it.
• Hotter objects emit more radiation, with more radiation being emitted every second.
• A higher temperature causes an object to emit some energy as visible light.
• Temperature of an object increases when it absorbs radiation faster than it emits radiation.
• Temperature of an object decreases when it emits radiation faster than it absorbs radiation.
• Temperature of Earth depends on rates of emission and absorption of radiation and reflection of radiation into space.
• Clouds reflect some radiation before it reaches Earth’s surface.
• Earth cools at night because radiation is emitted and not absorbed.
• Clouds keep the night sky warmer for longer.
• Electromagnetic waves are transverse waves that transfer energy from a source to an absorber.
• Electromagnetic waves form a continuous spectrum.
• Electromagnetic waves are grouped by wavelength.
• The six groups of electromagnetic waves are Microwave, infrared, visible light, ultraviolet, X-rays, and gamma rays.
• The five properties of electromagnetic waves are that they are transverse waves, travel through a vacuum at the same speed, obey the equation v=fl, transfer energy from one place to another, and mean that different wavelengths are absorbed, transmitted, refracted or reflected by different substances in different ways.
• Light refracts when it enters and leaves glass or water because the speed of light is greater in air than it is in glass or water.
• Electrons oscillate in a transmitting aerial when a high frequency alternating potential difference is applied.
• Energy in a wave is carried by electric and magnetic fields.
• A transverse wave is when oscillations are at right angles to the energy transfer.
• When radio waves are absorbed by a receiving aerial, an alternating current is created with the same frequency as the radio wave itself.
• Infrared radiation produces a heating effect.
• Ultraviolet waves are used in energy efficient lamps.
• Radiawaves are suitable for transmissions around earth’s surface due to their long wavelengths.
• Sound waves set our eardrums in motion which then set up vibrations in bones, allowing us to detect sound.
• Microwaves are used in satellite communication and cooking food.
• Warm objects emit infrared waves.
• When waves are transmitted, they change direction.
• Electromagnetic waves allow us to see and enable communications via phone, internet, television and radio.
• Wavelength is the distance between two adjacent peaks or two adjacent troughs.

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• Sound waves are sets of compressions and rarefactions in air.
• The normal line is a position drawn at 90 degrees to a surface where waves are incident.