Notes

light acts like a stream of particles called PHOTONS.

light behaves like waves

Electromagnetic radiation includes gamma rays,
X-rays, ultraviolet light, visible light, infrared radiation,
microwaves, and radio waves.

arrangement of these waves according to their wavelengths and
frequencies is called the Electromagnetic Spectrum.

motion is characterized by a property known as Wavelength, distance
from one wave crest to the next.

Shorter wavelengths have more energetic photons

blue light has more energetic photons than does red light.

theory of light—the wave theory or the particle theory—is correct

George Abell, “The mistake is only to apply them to situations
that are outside their range of validity.

Sir Isaac Newton used a prism to disperse visible light into its component colors,

Spectroscopy is the study of the properties of light that depend on wavelength.

Continuous spectrum is produced by an incandescent solid, liquid, or gas under high pressure.

Absorption spectrum is produced when visible light is passed through a relatively cool gas under low pressure

Emission spectrum is produced by a hot gas under low pressure.

When the spectrum of a star is studied, the spectral lines act as “fingerprints.”
These lines identify the elements present and thus the star’s chemical composition.

sun contains thousands of dark lines 60 elements

Doppler effect refers to the perceived change in wavelength of a wave that is emitted from a source that is moving away or toward an object.

The sonic boom occurs because some of the sound wave fronts arrive at the same instant
Approaching shorter wavelength
Receding Longer wavelength

In astronomy, the Doppler effect is used to determine whether a star or other body in space is moving away from or toward Earth.

Larger Doppler shifts indicate higher speeds; smaller Doppler shifts indicate slower speeds.
moving toward blue
moving away red

noted for an approaching object and is seen as blue light. A longer wavelength is noted for a receding object, which is seen as red light.