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Light and spectroscopy

Light and spectroscopy. Demonstration. What information can we gather from the demo with the prism?. Demonstration. So, what is white light made out of???. Visible Spectrum. The colors that we can see that make up white light 400 – 700 nanometers A quick aside on wavelengths and light…

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Light and spectroscopy

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  1. Light and spectroscopy

  2. Demonstration • What information can we gather from the demo with the prism?

  3. Demonstration So, what is white light made out of???

  4. Visible Spectrum • The colors that we can see that make up white light • 400 – 700 nanometers • A quick aside on wavelengths and light… • Definition of a wavelength • Light as a wave vs. a particle • Light is a form of ENERGY! • Electromagnetic radiation – When a particle gets excited, it gives off energy in specific wavelengths. This energy is known as…

  5. Visible Spectrum Continued • Only a PART of the electromagnetic spectrum • What on EARTH is this??? Ideas??? • The range of waves given off by particles arranged by their wavelength

  6. The Electromagnetic Spectrum

  7. Question? • Which side of the electromagnetic spectrum (EM spectrum for short) do you think has more energy? Why? Give evidence to support your answer.

  8. Spectrums • Three types of spectrums • Continuous • Absorption • Emission • Depending on what happens to the object, it will give off waves of light that will categorize it in one of the three types of spectrums

  9. Continuous Spectrum • What is an incandescent solid? • A solid that emits light because it is being heated. • When an object (of any phase) is heated, it gives off energy, in the form of LIGHT. when looked at with the correct tools you will see the visible spectrum. • The color of the object indicates its temperature. • Which is hotter – a red star or a blue star?

  10. Absorption Spectrum • When an electron GAINS energy, it only can absorb energy at SPECIFIC wavelengths. • The wavelengths absorbed are SPECIFIC to EACH element / compound. • The wavelengths absorbed will appear as black lines, from the continuous spectrum. • Under what conditions does visible light produce an absorption spectrum? • When it is passed through a cool gas under low pressure.

  11. Absorption Spectrum

  12. Emission Spectrum • When an electron LOSES energy, it emits it, but only at SPECIFIC wavelengths, specific to the element • Those emitted will appear on the continuous spectrum, but the rest will remain black. • Under what conditions is an emission spectrum created? • When a hot gas is under low pressure.

  13. Emission Spectrum

  14. The Doppler Effect • What happens when an ambulance drives by with its sirens on? • This is the doppler effect! • Why does this happen? • Sound is a form of energy. The pitch of the sound has a specific wavelength. • Wavelengths are compressed as it approaches the observer, which makes the pitch higher. • Wavelengths are stretched out as they leave the observer, which makes the pitch lower.

  15. How does this relate to light? • The same principle occurs with light waves, which are just another form of energy waves. • BUT , instead of hearing a higher / lower pitch, we might observe a higher / lower wavelength • What does it mean for an object to have a blue-shift? A red-shift? • What does it mean if the change in frequency is larger? (Think back to the ambulance, when does the pitch get the highest?)

  16. Why is this important? • Light is a form of ENERGY • Heat is a form of ENERGY, and is given off at specific wavelengths of the EM SPECTRUM • Stars and other objects give off LIGHT AND HEAT, at specific frequencies • How could we use this information? • To determine the chemical make-up of stars • To determine the speed of galaxies, if moving at all, and their direction relative to us.

  17. Chemical Make-up • What type of spectrum would a star give off? • Absorption spectrum • Why? • Each element in a star gives off specific wavelengths. Since the composition of each star will be slightly different, a spectrum given off by a star will be unique to it, just like a human’s fingerprint! • The color of the star (heat radiated off by the star) indicates its temperature.

  18. Galactic Motion • Edwin Hubble, a famous astronomer, discovered that galaxies have a huge red-shift. • The further the galaxy was away from us, the larger the red-shift it had. • What conclusions can we make from this? • The universe is expanding!!!

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