Day 6 Notes

Louis Lackey

Day 6 Notes

EMAIL ACCESS CODES TO MR CANTORAL

We began by watching a lecture by Alex Filipenko about black holes.

Chapter 5 is about light.

Section 5.1 is about the basic properties of light and matter.

Light is an electromagnetic wave. A particle of light is called a photon. Each photon has a wavelength and a frequency. The energy depends on its frequency. Light acts like both a wave and a particle. The electromagnetic spectrum is the span of wavelength and frequency. The speed is constant, and the wavelength and frequency of the wave are dependent on each other. The wavelength is between the crests, the amplitude is the difference in height between a crest and a trough, and frequency is the number of crests that pass a point in a second.

wavelength*frequency=speed of light=3*10^8 m/s

E=h*frequency

h=6.626x10^-24, planck's constant.

Matter is atoms. The isotope is a varying number of neutrons. Molecules are composed of multiple atoms.

Light and matter interact through emission, absorption, transmission, and reflection.

Emission-producing light

absorption-consuming energy

transmission-allows to pass through. Combination of both above.

Reflection-light bouncing.

Light is energy, light comes in many colors that combine to form white light. Types of light are infrared, visible, ultraviolet, X rays, and gamma rays.

Section 5.2 is about learning from light

There are three types of spectra. Spectra of an object are usually combinations of the three types. A span without interruption is a continuous spectrum. A cloud of gas will emit certain combinations based on its composition, called an emission line spectrum. Similarly, it will absorb certain combinations, called absorption line spectrum.

Each type of atom has a unique set of energy levels, regarding ionization. Each transition corresponds to a unique photon energy, frequency, and wavelength. Downwards transitions produced a unique pattern of emission lines. Because atoms absorb photons with those same energy’s, upward transitions produce a pattern of absorption lines at the same wavelength. Each type of atom has a unique spectral fingerprint. Observing all the fingerprints tell us what kinds of atoms are present in an object.

An object's thermal radiation spectrum depends on only one property- its temperature. Think of a poker in a fire. Hotter objects emit more light in all frequencies and photons with a higher average energy.

The Doppler effect tells the speed of an object. When an object is moving towards or away an observer, the frequency of the wave get squished or stretched.