Chapter 5.1 Notes

Chapter 5:

Light

The Cosmic Messenger

Spectrum

The light from the sun as it appears when we pass it through a prism or similar device.

What is Light?

Light is also known as electromagnetic radiation.

Wavelength

The distance between adjacent peaks.

Frequency

(The longer the wavelength of light, the lower its frequency and energy.)

Photons

Light comes in "pieces" called photons, each with a precise wavelength, frequency, and energy.

Infrared

Light with wavelengths somewhat longer than red light. It lies beyond the red end of the rainbow.

Radio waves

The longest wavelength light.

Microwaves

The region near the border between infrared and radio waves, where wavelengths range from micrometers to millimeters.

Ultraviolet

Light with wavelengths somewhat shorter than blue light.

X rays

Light with even shorter wavelengths.

Gamma Rays

The shortest wavelength of light.

-Radio waves, microwaves, infrared, visible light, ultraviolet, X rays, and gamma rays are all forms of light.

What is matter?

Each chemical represents a different type of atom, and atoms are in turn made of particles that we call protons, neutrons, and electrons.

Nucleus

Found at the center of the atom.

Electrical charge

A fundamental physical property that describes how strongly an object will interact with electromagnetic fields.(The properties of an atom depend mainly on the electrical charge in its nucleus.)

Atomic number

Atoms of different chemical elements have different numbers of protons in its nucleus.

Atomic Mass Number

The combined number of protons and neutrons in an atom.

Isotopes

Versions of an element with different numbers of neutrons. (Isotopes of a particular chemical element all have the same number of protons but different numbers of neutrons.)

Molecules

Atoms can combine to form molecules. (The number of different material substances is far greater than the number of chemical elements because of the molecules.)

How do light and matter interact?

-Matter can emit, absorb, transmit, or reflect light.

Emission

A light bulb emits visible light, the energy of the light comes from an electrical potential energy supplied to the bulb.

Absorption

When you place your hand near an incandescent light bulb, your hand absorbs some of the light, and this absorbed energy warms your hand.

Transmission

Some forms of matter, such as glass or air, transmit light, which means allowing it to pass through.

Reflection/Scattering

Light can bounce off matter, leading to what we call reflection (When the bouncing is all in the same general direction) or scattering (When the bouncing is more random).

(Materials that transmit light are said to be transparent, and materials that absorb light are called opaque.)