Optics & Waves

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Electromagnetic radiation is the type of energy that propagates through a vacuum. Different portions of the electromagnetic spectrum are known by different names, such as light, heat and radio waves, but are all part of the same phenomenon.

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  • How does a kaleidoscope work?

    Q: How does a kaleidoscope work?

    A: A kaleidoscope works by reflecting light that bumps into a reflective surface such as a mirror. It has two or more mirrors placed at an angle to each other. The mirror assembly is surrounded by a case, with an eyehole at one end of the mirrors and a collection of objects at the other end.
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  • What are light waves?

    Q: What are light waves?

    A: Light is made up of billions of tiny particles known as photons, which travel from one place to another place in waves known as light waves. Visible light waves are the only electromagnetic waves that the human eye can see. These waves are visible as the seven colors of the rainbow known as red, orange, yellow, green, blue, indigo and violet.
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  • What does the loudness of a sound depend on?

    Q: What does the loudness of a sound depend on?

    A: Loudness is a subjective measure of sound because it is dependent upon the qualities of the sound receptor. Although loudness is related to decibel levels, sound pressure, frequency, bandwidth and duration, the actual perception of the sound is the proper variable for determining loudness.
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  • Why are sound waves classified as mechanical?

    Q: Why are sound waves classified as mechanical?

    A: Sound is classified as a mechanical wave because it requires a medium to propagate its energy and cannot be heard in vacuum. There are two broad classes of waves - mechanical and electromagnetic. One requires a medium to be heard, and the other does not.
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  • What causes a mirage?

    Q: What causes a mirage?

    A: A mirage occurs when the air density difference caused by extremely hot temperatures causes photons to travel in a path other than a straight line. Hot air is less dense than cold air, so if there is a significant temperature gradient, the light reflected from an object may be refracted. This can distort the image.
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  • Why are lasers red?

    Q: Why are lasers red?

    A: Lasers are mostly red in color because red has the longest wavelength, approximately 650 nanometers. Because of this, red does not scatter easily and can be viewed from a long distance.
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  • How is light dispersed through a prism?

    Q: How is light dispersed through a prism?

    A: White light bends or refracts as it enters and exits the triangular prism, with shorter wavelengths bending the greatest amounts and longer wavelengths refracting less, resulting in a light spectrum of different colors like a rainbow. Prisms are made of glass or other transparent material and cut so the angle of entry and exit maximize this effect.
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  • What is an instrument that separates light into various wavelengths?

    Q: What is an instrument that separates light into various wavelengths?

    A: A prism is an instrument that separates light into various wavelengths. Visible white light contains light of many different wavelengths. When white light passes through a prism, each wavelength bends at a different angle to produce a rainbow effect with each wavelength of light displayed in its own band.
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  • Who invented the Doppler Effect?

    Q: Who invented the Doppler Effect?

    A: The Doppler Effect was proposed by Austrian physicist Christian Doppler in 1842. The theory was tested in 1845 by Dutch meteorologist C.H.D. Buys Ballot. Ballot's findings were supported by Scottish scientist John Scott Russell in 1848.
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  • Why do lights appear to flicker from a distance?

    Q: Why do lights appear to flicker from a distance?

    A: The flickering or twinkling effect of lights when observed from a distance is caused by anomalous refraction as light passes through air, schlieren, where temperatures and densities vary. The technical term for this phenomenon is called "scintillation," and it refers to the rapid changes in the position and color of a distant object.
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  • What is the difference between frequency and pitch?

    Q: What is the difference between frequency and pitch?

    A: Frequency refers to the number of vibrations that an individual particle makes in a specific period of time -- specifically, how often a wave peak goes by. Pitch, on the other hand, refers to the sensation of a frequency -- specifically, how high or low the frequency sounds.
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  • What is the definition of resonant frequency?

    Q: What is the definition of resonant frequency?

    A: Resonance frequencies are the natural frequencies at which it is easiest to get an object to vibrate. While setting up vibrations at other frequencies is possible, they require much more energy and constant input to maintain than a resonance frequency. Most objects have several resonance frequencies, and this property must be taken into account because of their positive, as with musical instruments, or negative, as with bridges, effects.
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  • What is the speed of light in water?

    Q: What is the speed of light in water?

    A: The speed of light in water is approximately 225,000 km per second. While enormously fast, this is notably slower than the speed of light in a vacuum, which is 300,000 km per second.
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  • How do X-rays work?

    Q: How do X-rays work?

    A: X-rays work by passing electromagnetic radiation through the body to create an image on film or on a digital device, thus providing diagnostic imaging. They are a part of the electromagnetic spectrum that includes visible light, ultraviolet light and infrared red heat. X-rays are shorter in wavelength than visible light and heat.
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  • How do convex mirrors work?

    Q: How do convex mirrors work?

    A: Convex mirrors work by reflecting parallel rays of light as if they all emanated from a single point somewhere behind the mirror. The distance between the actual surface of the mirror and this point depends on the level of curvature, with greater curvature resulting in lesser distance. Images in convex mirrors are distorted, with progressive compression of the image away from its center.
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  • How does a bell make sound?

    Q: How does a bell make sound?

    A: As the clapper of the bell strikes its sides, it causes them to vibrate, setting up a disturbance in the equilibrium of the air surrounding the bell. This disturbance travels through the air in a wave form that humans know as sound.
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  • How do waves carry energy from one place to another?

    Q: How do waves carry energy from one place to another?

    A: Energy is transferred in electromagnetic waves by vibrations in electric and magnetic fields. The vibration of air particles is energy transfer in sound waves, while the transfer of energy in water waves is the oscillation of water particles.
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  • What is energy that can move through empty space?

    Q: What is energy that can move through empty space?

    A: Electromagnetic radiation is the type of energy that propagates through a vacuum. Different portions of the electromagnetic spectrum are known by different names, such as light, heat and radio waves, but are all part of the same phenomenon.
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  • What makes sound waves?

    Q: What makes sound waves?

    A: Mechanical motion forms through the sound waves made by vibrating massive objects. Guitar, harp or piano strings are clear examples of the principle, but horns, percussive instruments and woodwinds also create vibrations that make sound waves. Even ordinary objects create sound waves if they vibrate.
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  • What are the uses for concave lenses and convex lenses?

    Q: What are the uses for concave lenses and convex lenses?

    A: Concave lenses are used for correcting myopia or short-sightedness. Convex lenses are used for focusing light rays to make items appear larger and clearer, such as with magnifying glasses.
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  • What is light made of?

    Q: What is light made of?

    A: The exact composition of light has eluded physicists for years, but the predominant theory is that light is comprised of a kind of energy called electromagnetic radiation. This energy behaves like a wave and a particle in different situations. Scientists believe electromagnetic radiation is composed of bundles of energy called photons.
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