Sound and Light

Sound Sound is a mechanical wave that is vibrations transmitted through matter (solid, liquid, or gas) The movement of the air molecules around a vibrating object is a sound wave

How does sound travel? Sound travels in waves As sound travels away from an object the waves become weaker Bill Nye “Waves” video clip: http://www.youtube.com/watch?v=OGyRe_SGnck

A CYCLE is the complete back & forth motion of a vibration Parts of a Sound Wave A CYCLE is the complete back & forth motion of a vibration

amplitude, crest, trough, wave and cycle Lets build a sound WAVE! What you will need: Yarn or string Scissors Glue Colored pencils Directions: Use your yarn/string to make the shape of a sound wave and glue it on your paper. Label the following parts: amplitude, crest, trough, wave and cycle

Intensity and Volume of Sound Intensity is the strength of a sound (measured in decibels) Volume is the loudness or softness of a sound FYI: Sounds above 130 decibels can damage your ears!

Pitch Pitch is the frequency of a sound (measured in hertz) high frequency = high pitch (example: flute) Low Frequency = low pitch (example: tuba)

Sound and Matter Sound cannot travel if there are no molecules of matter for it to travel through Sound causes particles of matter in air, liquid, or solids to vibrate and bump into another particle…think of it as the “domino effect” Sound travels more quickly through substances with molecules that are closer together

Try it out Try lining up dominoes close together and then farther apart. Which moves faster? This simulates how sound moves through particles that are closer and farther apart.

Sound and Temperature In higher temperatures, sound moves more slowly since the air particles are farther apart

Try it out Rules: no running and no shoving! Form two lines of people across the pod One line will have people an arm’s length away representing cooler air (cool air is more dense) The other line will have people 10 feet away from each other representing warmer air (warmer air is less dense) The goal: start at one end and touch the next person in line one by one until you get to the end. The line that gets to the end first wins This shows how sound travels through matter of different temperatures

You can calculate the distance of a storm! When you see a flash of lightening, count the number of seconds until you hear the thunder Divide the number of seconds by 5 seconds per mile The answer will tell you how many miles away the storm is! It takes 6 seconds to hear thunder after a flash of lightening. How far away is the storm? 6 seconds divided by 5 seconds per kilometer The storm is 1.2 kilometers away!

You can calculate the distance of a storm! The purpose of this experiment is to watch lightning and hear thunder to give you clues about how far away you are from a storm. Materials: One “thunderstorm” A stop watch (or the ability to say "one-Mississippi") After you see a flash of lightning, count the number of seconds until you hear the thunder. (Use the stop watch or count "One-Mississippi, Two-Mississippi, Three-Mississippi," etc.) 2. For every 5 seconds the storm is one mile away. Divide the number of seconds you count by 3 to get the number of miles. http://soundbible.com/tags-thunder.html

Questions to Discuss 1. What travels more quickly, light or sound? Why? If you said light travels faster than sound, you're right! The lightning and thunder are happening at the same time, but light reaches you instantly, while sound takes longer. 2. Do you ever see lightning without hearing thunder? Why is that? Some call that "heat lightning," but it is really lightning that is over 15 miles away and too far away for you to hear the thunder! LOOK OUT if you see the lightning and hear the thunder at the same time!

Sound is bouncy! Sounds can bounce off objects If a sound bounces back it is said to be reflected Sound that bounces back is called an echo Echos can be heard best when sound bounces off hard smooth surfaces

Using Sound in Science We can use echo sound to find object below the surface of water…this is called sonar We can use sound waves to see inside the human body…this is called an ultrasound

Let There Be Light! Light is a form of energy that can be seen We see objects only because light is reflected off of them Light is made of bundles of energy called photons Photons are tiny particles—a single photon is way too small to be seen

Light Waves Like sound, light travels in waves Light waves move like waves in water Light waves travel FAST! 300,000 km per second!

Parts of a Light Wave Crest Trough

Visible Light Light you see from the sun is “white light” White light is made up of a band of colors called the “Visible Spectrum”…you can see these colors when you see a rainbow You can use a prism see the colors in white light

Try It out! Make your own prism activity

Light is Bouncy! Light bounces back or reflects when it hits an object The only reason we can see objects is because they reflect light You can see an image in a mirror because light waves are reflected

Different Types of Mirrors Plane—a flat smooth surface Concave – this has a surface that curves inward…like the inside of a spoon Convex – this has a surface that curves outward…like the back of a spoon For a demonstration visit: http://youtu.be/JBi3PWrsKlg

Plane Mirrors This type of mirror gives the clearest image because the light reflects directly back

Concave Mirrors FYI: The focal point is the point where reflected light rays from concave mirror come together in front of the mirror If the image is located beyond the focal point of the mirror, it will appear upside down (inverted) If the object is in front of the focal point of the mirror, it will appear right side up If the object is at the exact focal point it will not appear at all!

Convex Mirrors This type of mirror creates an image that looks smaller than the real object Though the image is smaller, you can see much more area in a convex mirror…this is why convex mirrors are used a lot in store to help employees monitor retail areas

How is Light Bent? Refraction – the bending of a wave as it moves from one material to another Refraction Mini Lab!

Take a moment to explore concave/convex lenses! Lens - a curved piece of clear material that refracts light waves Concave Lens – light that passes through this lens are spread apart Convex Lens – Light that passes through this lens is refracted inward (the human eye has a convex lens) Take a moment to explore concave/convex lenses!

Nearsighted and Farsighted Nearsighted – able only to see things clearly that are close up Farsighted – able only to see things clearly that are at a distance

Scattering Light Waves Lab!