1. Sound, Light, Electromagnetic Spectrum and Mirrors

2. Sound Sound waves are compressional waves.
Two regions: compressions and rarefactions
Sound travels faster in liquids and solids than in gases.
Why? The molecules in liquids and solids are closer together.

3. Sound Humans hear sound waves in a limited frequency range.
20 Hz-20,000 Hz
Other ranges: dolphins 70 Hz-150,000Hz
Dogs 40 Hz-46,000 Hz
Infrasound-any sound lower than 20 Hz
Ultrasound- any sound higher than 20,000Hz
Ultrasound imaging is used in medicine
Sonar- is a system that uses reflected sound waves to determine distances & location of objects
Bats use sonar to navigate in flight & locate food

4. Ultrasound imaging used in medicine-echoes of very high frequency ultrasound waves between 1million-15 million Hz are used to produce computerized images called sonograms.
Bats use sonar to navigate in flight & locate food

5. Loudness is determined by…
the amount of energy in the wave
As the energy ↑, the amplitude of the wave will ↑
Your distance from the source the sound waves
Intensity of a sound describes its loudness
Intensity is measured in decibels(dB)

6. The Doppler Effect
The observed change pitch or wave frequency due to a moving wave source.
You hear the high pitch of the siren of the approaching ambulance, and notice that its pitch drops suddenly as the ambulance passes you. That is called the Doppler effect.
Pg 331 Figure 9

7. Doppler Effect The sound is louder due to wave compressions
The sound is lower due to wave rarefactions.

8. Electromagnetic Waves
Electromagnetic waves are made by vibrating electric charges and can travel through space where matter is not present.
Electromagnetic waves do not require a medium.

9. The Electromagnetic Spectrum
Gamma rays –short wavelengths and high frequency- very powerful and dangerous
Radio waves-long wavelengths & low frequency

11. The Nature of Light: Wave-Particle duality
Light can be modeled as a wave
Light waves which are electromagnetic waves consists of changing electric & magnetic fields
Light waves may reflect when they meet a mirror, refract when they pass through a lens, or diffract when they pass through a narrow opening.
Light can be modeled as a stream of particles
Photons- are a particle of light/bundle of energy

12. The speed of light depends on the medium!
Speed of light (c) = 3 x 108 m/s (in a vacuum)
Light is the fastest signal in the universe
Nothing can travel faster than the speed of light.
When light travels through different media, it slows down.

13. The speed of light depends on the medium! Medium Vacuum 2.997925 Air
Speed of light (x 108 m/s)
Vacuum
Air
Ice
2.29
Water
2.25
Quartz
2.05
Glass
1.97
Diamond
1.24

14. Mirrors Flat mirrors form virtual images by reflection.
When you look into a mirror, you see an image of yourself behind the mirror.
Virtual image is an image that forms at a point from which light rays appear to come but do not actually come
Real image is an image of an object formed by many light rays coming together in a specific location.

15. Types of Mirrors Curved mirrors can distort images
Since the surface is not flat, the line perpendicular to the mirror (normal) points in diff. directions for diff. parts of the mirror.
Mirrors that bulge out are called convex mirrors
Mirrors that are indented are called concave mirrors
Concave mirrors create real images.