Monday March 2 Tuesday March 3 Unit Question What do we know about the universe? How do we know it? Guiding Question / Learning Target How do we know what we know about the universe? Warm-up What is a mechanical wave? Agenda 1.TEST 2.Herschel 3.Em Notes Homework STUDY GUIDE DUE NOW! Disturbance in matter that carries energy through medium

Test! Study guide due! Notes and calculators! NO PHONES WHILE TESTS ARE OUT Turn in Math and any other missing work for mechanical waves. Last Day! (did you check no-name folder?)

Exploring the Visible Spectrum The Herschel Experiment William Herschel conducted first conducted this experiment in 1800 He was a famous astronomer that discovered the planet Uranus Herschel Experiment Gizmo Record the temperatures on your worksheet

Herschel’s Experiment Herschel used a prism to create a rainbow. He placed thermometers in different parts of the colors and beyond (where there was no color), and recorded temperature changes over time.

21 Start. All temperatures in  C

Minute. All temperatures in  C

Minutes. All temperatures in  C

Minutes. All temperatures in  C

Minutes. All temperatures in  C

Minutes. All temperatures in  C

Change in temp? What is difference start to finish?

Herschel Experiment Questions What did you notice about your temperature readings? Are there any trends? Where was the highest temperature increase?

What do you notice about your temperature readings? As time increases temp increases As you go toward red, temp change increases Where was the highest temperature change? Beyond red

Herschel Experiment Questions What do you think exists beyond the red part of the spectrum? The highest temperature is beyond the red light There must be some kind of radiation we can’t see! This unknown radiation is called Infrared Radiation Before Herschel’s experiment scientists did not know about other types of radiation

Stars and galaxies don’t emit only visible light. The images below show the same region in space but with a detector for different EM wavelengths. These pictures are of the crab nebula, the remnants of a an exploded star.

Light, Waves and the Electromagnetic spectrum

Waves… a review Most waves are either longitudinal or transverse. But all electromagnetic waves are transverse.

Electromagnetic Waves Also known as EM waves Produced by the movement of electrically charged particles Can travel in a “vacuum” They do NOT need a medium Travel at the speed of light = 300,000 km/s

Wave-particle Duality Light can behave like a wave or like a particle A “particle” of light is called a photon.

Electromagnetic Spectrum The electromagnetic spectrum represents the range of energy from low energy radio waves with long wavelengths up to high energy gamma waves with small wavelengths. The longer the wavelength, the less the energy. lowest energy Highest Energy

Visible light is a small portion of this spectrum. R ed O range Y ellow G reen B lue I ndigo V iolet ROY G BIV

Astronomers Study Light Light is made up of different colors Color Vision (web) Color Vision Color Vision (local) Color Vision

What happens to the light that enters the prism? Do all the colors bend the same way? Does the light get bent only once?

The Visible Spectrum

Different Colors of Light All light travels at the same speed regardless of its color. 186,000 miles per second. That’s the length of your ruler in 1 nanosecond!

The Sun emits most of its electromagnetic energy in the visible light part of the spectrum— our eyes have evolved to take advantage of the available “VISIBLE” light. Visible light is the only EM wave that our eyes can detect.

From R-L: The same flower with human vision, only UV vision (bright = UV), simulated bee vision (UV+G+B), simulated bird vision (tetrachromatcic: UV+R+G+B). (Photos: (c) Dr Klaus Schmitt, Weinheim, Germany, uvir.eu )uvir.eu

Infra red image of a mouse – snakes can detect infra red (heat) that humans cannot. Most IR images are false-color to identify areas that are warmer (red) and cooler (blue/green)

IR is also part of thermal-imaging night vision technologies.