Energy, Energy Transformations

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Light is also an electromagnetic wave

The wavelength is the distance between adjacent peaks of the electric or magnetic field

1 nm (nanometer) = 10–9 m 1μm (micron) = 10–6 m

The frequency is the number of peaks that pass by any point each second, measured in cycles per second or Hertz (Hz).

light demo

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Light is an electromagnetic wave

Light consists of many individual photons.

Each travels at the speed c and can be characterized by a wavelength and a frequency.

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Many Forms of Light

The spectrum of light is called the electromagnetic spectrum

Different portions of the spectrum are called:

The visible light - what we see with our eyes

The infrared light - beyond of the red end of rainbow

The ultraviolet light - beyond the blue end

Radio waves - light with the longest wavelengths

X rays - wavelengths shorter than ultraviolet

Gamma rays - the shortest wavelength light

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Electromagnetic spectrum

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Electromagnetic spectrum

Frequency units – Hertz

1 Hz = 1 c1

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Light and Matter

The amount of light is called intensity

Studying spectra of celestial bodies one can learn a wealth of information about them

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Atomic Structure

92 chemical elements have been identified in the Universe.

Nearly 20 more have been created artificially.

Each chemical element is made from a different type of atom.

Atoms are made from particles called protons, neutrons, and electrons.

Protons and neutrons form the nucleus in the center of the atom.

Electrons surround the nucleus.

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Atomic Structure

Positively charged protons are hold together by the strong force, which overcomes electrical repulsion.

Negatively charged electrons are attracted to the nucleus.

The number of protons in an atom is called the atomic number, which is unique for different chemical elements.

The combined number of protons and neutrons in an atom is called the atomic mass number.

Atoms of the same element with different number of neutrons are called isotopes.

Slide 18

Absorption and Emission in Gases

Since electrons in atoms can have only specific