Visible Light The light we see visible light

Visible Light The light we see (visible light) only spans about 1. 5% of electromagnetic spectrum.

Spectral Patterns • white light splits into bands of colours as it passes through a prism called the visible spectrum • light from distance stars can be collected and divided into individual spectral patterns (a galaxy fingerprint)

3 Types of Spectra 1. Continuous Spectrum 2. Brightline Spectrum (Emission) 3. Darkline Spectrum (Absorption)

red orange yellow green blue ROYGBIV 1. Continuous Spectrum Continuous set of emission lines forming an unbroken band of colors from red to violet. • Produced by a glowing solid Ex. a Tungsten white light bulb, & white sunlight. Shows the source is sending out light of all visible wavelengths. indigo violet

2. Dark-Line Spectrum / Absorption Spectrum • Produced when a cooler gas lies between the observer and an object emitting a continuous spectrum • Example: 1. The atmosphere of planets 2. Outer layers of a star • The cooler gas absorbs specific wavelengths of radiation passing through it.

3. Bright-Line Spectrum / Emission Spectrum • Only specific wavelengths of light are emitted by hot gas – example Neon signs, black lights, LED’s Each element has its own unique spectra they can be identified by light (it’s fingerprint)

How Spectra are Produced

• as sound approaches the wavelength is compressed so the pitch is higher • as sound leaves the wavelength is stretched out so the pitch is lower • The same thing happens with light

Cosmological Spectral Shifts • As a galaxy moves away from earth the light emitted wavelengths increases (become longer). • This is known as a red shift • Now if its a blue shift it means the wavelength is getting shorter; the star is getting closer.