5-1 How we measure the speed of light

5-2 How we know that light is an electromagnetic wave

5-3 How an object’s temperature is related to the radiation it emits

5-4 The relationship between an object’s temperature and the amount of energy it emits

5-5 The evidence that light has both particle and wave aspects

5-6 How astronomers can detect an object’s chemical composition by studying the light it emits

5-7 The quantum rules that govern the structure of an atom

5-8 The relationship between atomic structure and the light emitted by objects

5-9 How an object’s motion affects the light we receive from that object

nature of light By reading this chapter, you will learn

Determining the Speed of Light

Galileo

Fizeau and Foucalt (1850) d=rt again gave c

Olaus Rømer (1676)

I. Newton - particle-like properties

C. Huygen – wave nature

Young’s Double-Slit Experiment – wave like properties (1801)

James Clerk Maxwell (1860s) wave nature: electromagnetism

• Because of its electric and magnetic properties, light is also called electromagnetic radiation

• Visible light falls in the 400 to 700 nm range

• Stars, galaxies and other objects emit light in all wavelengths

electromagnetic radiation around you

Three Temperature ScalesSee box 5-1 (pg. 105)

Temperature conversion

•Tf = 9/5 Tc +32

•Tc = 5/9 (Tf -32)

•TK = Tc + 273

How are you doing?1. Who was the first person to come up with a

method to measure a reasonable value of speed of light?

2. Huygen’s idea of light was light as _____, which was different from Newton’s view of light. A) particle, b) wave, c) part of electromagnetic radiation, d) photons of various energy level

3. Light part of electromagnetic radiation. What type of electromagnetic radiation is high energy? A) radio wave, b) visible light, c) Ultraviolet, d) infrared, e) gamma ray

Put the following color in the order of cooler to hotter:Yellow, Red, Orange, Blue, white

Black body radiationWien’s lawmax ~ 1/TempStefan-Boltzmann lawLuminosity ~ T4

Planck’s lawE ~1/ This is the method we

used to determine the surface temperature of the sun.@1AU, we receive 1370W /m2

Each chemical element produces its own unique set of spectral lines

Kirchhoff’s Laws

Doppler effect • Red Shift: The object is moving away from the observer

• Blue Shift: The object is moving towards the observer

Properties of light1. Which color is hotter? A) blue, b) red, c) yellow, d)

white

2. Which type of sprctra is produced by hot thin gas? A) continuous spectrum, b) absorption spectrum, c) emission spectrum

3. Longer wavelength means: a) higher energy, b) lower energy

4. Bohr model explains:

5. If a star is moving away from us, the star will suffer: a) blue shift, b) red shift, c) both blue and red shift.

6. If a star is rotating fast, the star will suffer: a) blue shift, b) red shift, c) both blue and red shift.