Go over 3 homework questions

Answer Key• 1. Draw a diagram showing what happens to white light when it passes through a prism.• 2. Sketch and label the parts of a wave. How does wavelength vary with color?• Red light has longest• wavelengths. Blue or violet• light has the shortest.• 3. Describe how Sir William Herschel showed that there are forms of radiation that we• cannot see with our eyes.• Herschel measured the temperatures of different wavelengths of sunlight. He spread• sunlight out into its component colors by passing it through a prism. He then put• thermometers in different colors of the spectrum and recorded their temperatures• over a few minutes. He found that the temperature was higher near the red end of the• spectrum than near the blue end. He also put a thermometer just beyond the red part• of the spectrum, where there was no visible light. He found that the temperature just• beyond the red was even higher than that near the red. Some kind of radiation that• we can’t see with our eyes was heating the third thermometer. Scientists now know it• was infrared radiation.• Credit: © Michael Guidry, University of Tennessee, Knoxville

• Many Faces of the Sun

Image Title Observations Additional Comments

#1 Sun in Visible Light

#2Infrared Sun Image

#3Radio sun Image

#4 Ultraviolet Sun Image

#5X-ray Sun Image

Radio Wave Image of the Sun

Visible Light Image of the Sun Infrared Image of the Sun

Ultraviolet Light Image of the Sun X-ray Image of the Sun

• The dark spots on two of the images and the bright spots on the other images are called sunspots.

• Why do you think these pictures are so different?

• That is what we will be investigating in this activity.

• Think back to Sir W. Herschel experiment with the thermometers in the rainbow colors.

• What did that experiment show?• Can you think of other types of radiation?– What causes sunburns?– How do you cook food quickly?– How do you look for broken bones?– What kind of radiation is in nuclear reactors?

VISIBLE LIGHT

How do wavelengths change along the spectrum?

•Different colors have different wavelengths, with red light having longer wavelengths than blue or violet light.•Infrared radiation is just beyond the red, at longer wavelengths than visible light.•Ultraviolet radiation is just beyond the violet, at shorter wavelengths than visible light.

Visible Light Region of the Electromagnetic Spectrum

Electromagnetic Spectrum

• Scientists have divided the electromagnetic spectrum into these different kinds of light, based on their wavelengths.

• Gamma rays have the shortest wavelengths - less than 0.01 nanometers 1 x 10-11 meters

• Radio waves have the longest wavelengths, defined as anything over about 10 centimeters

Electromagnetic Spectrum

SUN FACES• These pictures of the Sun look different because

they each show different wavelengths of energy that the Sun emits.

• The only way we can learn anything about the Sun and other astronomical objects is to study the light that comes from them.

• Studying light from different regions of the electromagnetic spectrum helps astronomers learn more about the Sun and other cosmic objects.

Radio Wave Image of the Sun

Visible Light Image of the Sun Infrared Image of the Sun

Ultraviolet Light Image of the Sun X-ray Image of the Sun

Scientists use different telescopes to take pictures of the Sun at different wavelengths; they can't use just one telescope to detect all

wavelengths.

Telescopes

Visible Light Image of the Sun Big Bear Solar Observatory(Southern California)

Infrared Light Image of the SunMcMath-Pierce telescope(Kitt Peak, Tucson, AZ)

Radio Wave Image of the SunNobeyama Radio Observatory

(Japan)

Ultraviolet Light Image of the SunSOHO

(Solar and Heliospheric Observatory)orbits the Sun

X-rayImage of the Sun

Yohkoh satellite(orbits the Earth)

TRACE satelliteTransition Region And Coronal Explorer

(orbits the Sun)

By the Light of a Star Student Activity SheetRead the questions below before you begin reading “By the Light of a Star.” Use your answers to the

questions to fill in the table . An example has been started for you.

1.What are the different kinds of electromagnetic waves, in order from shortest wavelength to longest wavelength?

Use your answers to fill in the column “Different kinds of electromagnetic waves.”

2. What is an example of each kind of electromagnetic wave that people use, or are affected by, in everyday life?

Use your answers to fill in the column “Everyday example of this wave.”

3. What is an astronomical example (example from astronomy) of each kind of electromagnetic wave?

Use your answers to fill in the column “Astronomical example of this wave.”

Wavelength Different kinds of electromagnetic waves

Everyday example of this wave Astronomical example of this wave

Shortest

Longest

Ultraviolet Causes Sunburns

Remember !!!!!

• That the only way that we can learn about the sun and other cosmic objects is to study the light that comes from them.

• Astronomers need telescopes to collect and study that light.

Problems that interfere with telescopes on the ground

The Problem How do astronomers reduce this problem ?

Light pollution : surrounding light from cities makes it harder to see objects

Build telescopes far away from city lights

Size of telescope ; the bigger the telescope , the more light it can gather

Build bigger telescopes

Heat and wind; both can make it harder to see details in distant objects with a telescope

Build telescopes in arid areas with stable air.

Clouds and fog; both can make it harder to see details in objects through a telescope

Build telescopes in arid areas with stable air.

Scattering of light by Earth’s atmosphere; particles in atmosphere scatter blue light more than red

Build telescopes on top of mountains above much of atmosphere or put telescopes in space.

Earth’s atmosphere prevents light at many wavelengths from

reaching the ground.

Rotating Sun

• Compare the image of the Sun on the right with that on the left, looking for changes.

Sun at X-ray Wavelengths

• The TRACE satellite has provided spectacular images and movies of the Sun taken at X-ray wavelengths.

QUIZ!

• There will be a quiz next class.• You should know– The types of waves ,in order of wavelength– How different types of waves are similar and

different– Different factors that affect observations made

with telescopes