# Spectra

Télécharger la présentation

## Spectra

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
##### Presentation Transcript

1. Spectra

2. White Light • Light from many colors mixes to form white light. • Different colors have different wavelengths. • Shorter wavelengths bend more through a prism. • A diffraction grating combines many edges and acts like a prism.

3. Emitted photon Moving electron Sources of Photons • Accelerated electrons and atoms emit photons. • Photons can be reabsorbed as well.

4. Temperature • Higher temperature means more energy. • Temperature is measured in kelvin (K). • Absolute zero: 0 K = -273 ºC = -459 ºF. • Room temperature: 300 K  20 ºC = 68 ºF. • Temperature of the Sun: 5800 K  6100 ºC  11,000 ºF • At high temperatures kelvin and centigrade are about the same.

5. Heated objects give off electromagnetic waves. Higher temperature has more radiation A hot object gives off a spectrum of frequencies. Shifts based on temperature intensity high energy low energy frequency Radiation from Heat

6. Radiation due a heated object is called blackbody radiation. Wien’s law relaters the temperature to the peak wavelength. intensity high energy low energy frequency Continuous Spectrum

7. Atoms and Light • An atom is a nucleus surrounded by electrons. • An electron can be in specific energy states. • Change from a high to low energy state produces a photon. • Atoms can also absorb a photon to excite an electron.

8. Discrete Spectrum • Each atom has its own set of energy levels. • Each atom generates photons at specific frequencies. • The pattern of frequencies (colors) identifies the atom. • Examples include neon or mercury lights. helium neon