Chapter 12 – Holt Science Spectrum

Sound and Light Waves

Journal – 1/5/2010

•Compare/Contrast reflection and refraction.

Journal – 1/6/10

• What causes bubbles to be so colorful and does the type of solution matter?

BUBBLESPlease write the following on your own paper to be

turned in at the end of class. (20 points)

• Q/P: What causes bubbles to be so colorful and does the type of solution matter?

• Hypothesis: If light __ off the outside and inside walls of the bubble then ___.

• Procedure: Develop your own

• Data: Record any and all observations.

• Conclusion: Were you right? What can you conclude? What would you change?

Bubbles continued

• Light is bouncing off (reflection) both the inside and outside surface of the bubble. When light waves from the inner and outer surfaces interfere with each other and produce brightly colored patterns. The electromagnetic light has a wide range of colors. Each color has a unique wavelength.

The Science Behind Bubbles• Liquid detergents reduce the forces between

water molecules letting bubbles form. In fact detergent molecules will cover the surface of a bubble and let it expand a great deal without breaking. A soap bubble actually is a sandwich of air on the inside, a layer of detergent molecules, a layer of water and finally another layer of detergent molecules.

Bubbles continued

• You see a particular color when the surface of the bubble is just the right thickness (one quarter wavelength thick) to cause constructive interference for a particular color. But when the surface of the bubble gets very thin the light destructively interferes and you see mostly black.

Journal – 1/12/10• No journal today – complete the science

survey and turn it in in the next 10 minutes in the homework basket.

• If you finish before everyone else please get a science book and turn to page 388 and begin the previewing Chapter 12 – hunt for the items listed on the board – record in your journal – your quiz on Friday – will be over the preview.

Quiz – 1/13/2010

• Turn to page 398 in your Science Spectrum book.

• Answer any 3 of the 10 questions. Each question is worth 3.33 points. You may do more if you choose.

• YOU MAY use your book.

• If you finish early read section 12.1 and take 2-column notes beginning on pg 390.

Answers• 1. state of matter, type of medium, temperature

• 2. Sound travels faster in water because the molecules (atom) are closer together; they can hit and collide with each other easier. In air, the atoms are very far apart.

• 3. Audible sound can be heard by the human ear (freq – 20Hz to 20,000Hz); Sounds lower than 20Hz make up infrasound. Sounds higher than 20,000 Hz are ultrasounds.

• 4. Frequency increases and wavelength decreases.

• 5. Amplitude and intensity both increase.

• 6.The two notes have the same pitch but they sound different because they emphasize different harmonics.

• 7. The acoustic guitar has a hollowed out section that vibrates in resonance with the string. Electric guitars have solid bodies that vibrate very little.

Answers continued.

• 8. Compressions and rarefactions in sound waves strike the eardrum, causing it to vibrate. The vibration is transferred to the 3 small bones found in the middle ear to the basilar membrane in the cochlea where they stimulate hair cells which stimulate nerves that lead to the brain.

• 9. Ultrasound vibrations travel easily through tissue, but audible waves do not.

• 10. As the strings vibrate, the sound board vibrates at the same frequency (resonance), causing stronger compressions and rarefactions in the air than the vibrating string would have caused alone. This produces a louder sound.

Journal – 1/14/2010

• What causes sound?

Journal – 1/15/2010• What are two ways you can describe a

wave?

• Complete the following statement about waves: “All waves follow one rule, if the frequency changes, the wavelength will………………………………”

Quiz – 1/15/2010

• 1. All sound waves are ___.

A. longitudinal B. transverse

C. electromagnetic D. standing waves

• 2. The speed of sound depends on __.

A. the temperature of a medium.

B. the density of the medium.

C. How well the particles of the medium transfer energy.

D. All the above.

• 3. How is the loudness of sound related to amplitude and intensity?A. The more energy applied to sound waves the louder the sound is.

B. The less energy applied to sound waves the louder the sound is.

C. The sound is loudest when no energy is applied.

D. None of the above.

Journal – 1/19/2010

• Define the following

• Frequency

• Loudness

• Intensity

• Diagram and trace the steps in how humans hear.

Journal – 1/20/2010

•Explain resonance and harmonics

Journal – 1-21-2010

• According to yesterday’s readings from the spectrometer, a couple of your statements were:

– “Light colors reflect more and darker colors absorb most of the light.”

– “When the same color light reflected off the same colored paper the reflectance reading was higher than the other readings from the other colored lights.”

Evaluate these statements – Tell me whether you agree or disagree. Back up your argument with your observations from the lab activity.

Journal 1/22/2010

•Why do we see color?

Journal 1-27-10When you look at the grass

outside, you see the color green. Explain, in detail, why you see

the color green and not the other colors of visible light?

Journal – 1/29/2010

Compare and contrast a virtual image and a real image.

Journal – 2/1/2010

• Describe how your eye allows you to see colors and images. (page 416)

ReviewConservation of Energy

Energy cannot be created or destroyed.It can only be changed from one form to another.

The above statement is called the law of conservation of energy

Sound – 12.1Page 390

Chapter 12Light and Atomic Structure

• Light and its properties

• Atomic structure

• Interaction between Light and Matter

• Spectrum

Light in Everyday Life

• Light is a form of energy, radiative energy

1 Watt = 1 Joule/sec

• Light has color

A prism split light into a spectrum (rainbow of colors)

Light travels with a speed of c = 300,000 km/s

Rainbow

Properties of LightLight behaves as both a particle and a wave

Light particles are called photons, which can be counted individually.

Light is also an electromagnetic wave

The wavelength is the distance between adjacent peaks of the electric or magnetic field 1 nm (nanometer) = 10–9 m 1μm (micron) = 10–6 mThe frequency is the number of peaks that pass by any point each second, measured in cycles per second or Hertz (Hz).

light demo

Light is an electromagnetic wave

Light consists of many individual photons.Each travels at the speed c and can be characterized by a wavelength and a frequency.

Many Forms of Light

The spectrum of light is called the electromagnetic spectrum

Different portions of the spectrum are called:

The visible light - what we see with our eyesThe infrared light - beyond of the red end of rainbowThe ultraviolet light - beyond the blue endRadio waves - light with the longest wavelengthsX rays - wavelengths shorter than ultravioletGamma rays - the shortest wavelength light

Electromagnetic spectrum

Electromagnetic spectrum

Frequency units – Hertz1 Hz = 1 c1

Light and MatterThe amount of light is called intensity

Studying spectra of celestial bodies one can learn a wealth of information about them

Atomic Structure

92 chemical elements have been identified in the Universe.Nearly 20 more have been created artificially.

Each chemical element is made from a different type of atom.Atoms are made from particles called protons, neutrons, and electrons.Protons and neutrons form the nucleus in the center of the atom.Electrons surround the nucleus.

Atomic Structure

Positively charged protons are hold together by the strong force, which overcomes electrical repulsion.

Negatively charged electrons are attracted to the nucleus.

The number of protons in an atom is called the atomic number, which is unique for different chemical elements.

The combined number of protons and neutrons in an atom is called the atomic mass number.Atoms of the same element with different number of neutrons are called isotopes.

Examples of Spectra

Temperature and Color

Temperature and Intensity

Reflected light

When the light (for example, sunlight) strikes anobject (ground, clouds, people), we see only thewavelengths of light that are reflected

Different objects (fruits, rocks, atmospheric gases)reflect and absorb light at different wavelengths

The Doppler Shift

Radial motion of a distant object can be determined due to the Doppler effect

The Doppler effect causes shifts in the wavelengthsof light

If an object is moving toward us, its entire spectrum is shifted to shorter wavelengthsBecause shorter wavelengths of the visible light are bluer, the Doppler shift of this object is called a blueshiftThe Doppler shift of a moving away object - redshift

Doppler Effect

Demo Doppler effect

Summary

Spectral information gives us more knowledge about the objects (composition, surface temperature, moving properties)

Visible light is only a small portion of the electromagnetic spectrum

The Doppler effect tells us how quickly light is moving toward or away from us