The angle of incidence beyond which a wave will undergo total internat reflection.
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Constant Temperature (H)
Bodies at a fixed temperature radiate the same average power that they absorb.
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Concave Lens
A lens that is thicker at the edges than in the centre. Parallel rays diverge when passing through.
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Convex Lens
A lens that is thicker in the centre than at the edges. Parallel rays converge when passing through.
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Diffuse Reflection
The reflection of a wave from a rough surface that results in the wave being scattered.
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Electromagnetic Spectrum
A group of transverse waves that cover a large range of frequencies and wavelengths. The highest frequency waves in the spectrum are gamma-rays and the lowest are radio waves.
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Electromagnetic Waves
Transverse waves that transfer energy from the source of the waves, to an absorber. They form a continuous spectrum of different frequencies and all travel at the same speed in a vacuum.
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Focal Length
The distance between the centre of a lens and its principal focus.
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Gamma Rays
High energy radiation rays used for detecting and treating cancers, and sterilising food and medical implements. They can cause cell damage and mutations.
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Infrared Radiation
A type of radiation that all objects emit and absorb. The hotter an object is, the greater the infrared radiation it emits in a given time.
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Infrared
Used for cooking food, thermal imaging and short range communications. It can cause skin burns.
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Law of Reflection
The angle of incidence must always equal the angle of reflection when a wave reflects.
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Lens
An object that forms an image through the refraction of light.
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Microwaves
Used for satellite communications and for cooking food. They can cause internal heating of body cells.
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Power of a Lens
Equal to the reciprocal of the focal length of a lens. Concave lenses have negative powers whereas convex lenses have positive powers.
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Principal Focus
The point before or after a lens where light rays appear to meet. The rays may converge or diverge away from this point.
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Radiowaves
Used for television and radio signals. They can be produced by oscillations in electrical circuits, or can induce these oscillations themselves.
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Ray Diagram
A visual representation of the path of a wave, usually around the point where it meets a boundary. Rays are usually drawn as straight lines with an arrow pointing in their direction of travel.
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Real Image
An image produced by light-rays physically converging. Real images are ones that can be projected onto a screen.
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Reflection
The bouncing back of a wave at a boundary.
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Refraction
The changing of speed, and consequently the direction, of a wave as it changes medium. The wavelength of the wave will also change but the frequency remains constant.
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Specular Reflection
The reflection of a wave from a smooth surface.
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Speed of EM Waves
All electromagnetic waves travel at the same speed in a vacuum, 3X10(8)m/s.
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Total Internal Reflection
A process that occurs when a wave meets the boundary from a medium with a high refractive index to one with a lower refractive index, at an angle of incidence greater than the critical angle. All the wave is reflected at the boundary.
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Ultraviolet
Used in energy efficient lamps, disinfecting water, and for sun tanning. It can cause cell and eye damage that can result in skin cancer and eye conditions.
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Virtual Image
An image produced by the apparent, but not actual, divergence of light-rays. Virtual images cannot be projected onto a screen.
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Visible Light
The only type of electromagnetic radiation that our eyes can detect. It is used for fibre optic communications and photography.
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X-Rays
Used for medical imaging and security scanners. They can cause cell damage and mutations.
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Other cards in this set
Card 2
Front
Constant Temperature (H)
Back
Bodies at a fixed temperature radiate the same average power that they absorb.
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