Light and Sound

Sound Sound is a longitudinal wave Sound causes compressions and rarefactions in the air molecules Sound must travel through a material Sound can not travel through empty space Decibels – how loud the sound is Decibels are determined by amplitude (energy)

Pitch of sound The pitch of the sound wave depends on the frequency of the wave High frequency is high pitch Low frequency is low pitch

Doppler Effect Sound Change in frequency and pitch of a sound that is caused by either the movement of the object or the listener Ambulance Race car

Speed of Sound Sound travels at 340 m/s in air Changes speed depending on how close together the atoms in the material are The speed of sound is different in different materials – Travels fastest in solids (steel – 4512 m/s) – Travels in between in liquids (water – 1483 m/s) – Travels slowest in gases Speed also depends on the temperature – Travels faster in warm air (100⁰F – 354 m/s) – Travels slower in cold air (0⁰F – 320 m/s)

Supersonic Caused by motion that is faster than the speed of sound Silence as the object is approaching Loud boom after the object passes Sound is racing to catch up

Light Light is created when electrons move energy levels inside of the atoms When energy is added to an atom the electrons jump to higher energy levels When electrons fall back to lower energy levels, energy is released in the form of light

Light Does not need a medium to travel through Can travel through empty space Speed is fastest in gas, slowest in a solid As the wavelength increases, the frequency decreases

Theories of Light Particle theory – light travels as streams of particles or photons in a straight line – reflection Wave theory – light travels as waves – light travels through openings and spreads out Quantum theory – a bundle of light energy (quantum) that travels in waves

Particles, Waves or Quantum

Speed of Light Speed of light is 300,000,000 m/s Light can circle the earth 27 times in 1 second Why do we see lightening before we hear thunder?

Photoluminescence Glow in the dark Atoms in certain materials can store energy when they exposed to light When the light is turned off they are no longer storing energy and energy is given off as light

Electric Light Electricity is used to cause the electrons to jump and fall between levels Incandescent bulbs heat metal to give off light- they also give of heat – less efficient Fluorescent bulbs heat gases to give off light – give off less heat – more efficient

Colors of Light White light is composed of all the colors of the spectrum – ROY G BIV – Light from the sun is white – what happens when it travels through a raindrop? Black light is the absence of all color – Shut yourself in the bathroom with no light – can you see any color?

Colors of Light Photoreceptors in the eye detect visible light The light we see is reflected light Why do we see color? – Light that hits the shirt from the sun or a light bulb is white – The color of an object depends on the light wave that is sent to our eye – A blue shirt looks blue because blue light waves are sent to our eye

Color in Art Do pigments mix the same way that light mixes If I mix all the colors of pigment do I paint with white paint How do I make white paint or have white paper?

Optics Lenses – use refraction to bend light Mirrors – reflect light Prisms – uses refraction to separate light into the colors Telescope – collection of lenses used to magnify an object Laser – one specific wavelength of light that is concentrated and organized