Invisible Light

F 116-122

How do waves move?

• All waves carry energy from place to place– The way the wave carries the energy depends on the

kind of wave motion– Particles of matter also vibrate back and forth along the

same direction– Without particles vibrating back and forth in the

direction the sound is traveling the sound vibration could not travel

• Sound waves can not travel in a vacuum (a space with no matter)

How do light waves travel?

• Electromagnetism forces that come from electricity and magnetism– magnets can set up a flow of electricity and

electricity can produce a kind of magnet

• The electrical and magnetic parts of the energy can carry themselves as a wave moving through space

• Electromagnetic waves can travel with ot without matter

• Electromagnetic waves vibrate back and forth across the direction in which light travels

• Light slows down when it travels through matter– It always travels much faster than sound

• That is why you will see lightning flash before you hear thunder crash

Electromagnetic Spectrum

• All of the wavelengths of light (the ones we can and cannot see)

Which wavelengths are longer than red?

• Radio Waves– The longest waves of the e.s– A.M. the height of the waves is changed to

carry the signal– The number of the radio station represents

the frequency at which the station sends out radio waves

• Radar– The echo waves helps animals locate things– Radar stands for: radio detecting and ranging– Uses radio waves that reflect off of many

objects • Used to help weather forecasters detect thick fog

and rain

• Microwaves– Shortwave radio waves– Water in foods absorb microwaves easily; the

energy from the absorbed waves speeds up the water molecules inside the food; this causes the food to heat up

• This is why microwaves heat food faster than a regular oven

• Infrared light– Means “just beyond red”– Next to visible red on the spectrum – When you stand in the sunlight the Sun’s

infrared waves warm you up– All object give off infrared waves depending

on their temperature• Warmer objects give off more than cooler objects

Which wavelengths are shorter than violet light?

• Ultraviolet Light– Made up of waves just shorter than visible

violet light– UV light causes chemical changes

• It can produce vitamin D for your body• It can also be harmful: it causes sunburn which

can lead to some forms of cancer

• X Rays and Gamma Rays– The shortest waves of

the spectrum and have the most penetrating power

• X rays pass through most objects; thicker or denser objects absorb the rays this is why an X ray of your bones can show a broken bone

What are lasers?

• Regular light from a bulb or a candle has many wavelengths all mixed together; as the light travels the waves get more spread out and less noticeable

• Lasers produce light that does not spread out or become weaker