Department of Mathematics and Science

Department of Mathematics and Science

Electromagnetic Spectrum

• 1) visible light: humans can see.• 2) Radio waves: carry signals to wireless devices

like cell phones or computers.• 3) Microwaves: when absorb the energy from the

waves the food become hot.• 4) Infrared: from the lamp keep the food warm.• 5) X-ray: bones absorb more than muscles orskin so they appear lighter.• 6) Ultraviolet: can harm your skin.

Department of Mathematics and Science

Department of Mathematics and Science

Light Waves•Light waves are different from sound waves. Sound waves travel as compressions in matter. Light doesn’t compress matter.•Light moves like Ocean waves. ( when the water moves up & down it doesn’t move forward or backward).•Hold 1 end of a rope & shake it up & down, you make a wave that moves along the rope, but the vibrations is across that direction forming an “ S” shape•This kind of wave is called “ transverse waves”.

Department of Mathematics and Science

Light Transverse Waves•Like compression waves. transverse waves carry only energy( the rope is still in your hand even though the energy has traveled away from you).•Light waves don’t need matter so it can travel through empty space. •Sun gives off visible light as well as other waves in the electromagnetic spectrum.•Waves travel through space & reach the Earth.

Department of Mathematics and Science

DID YOU KNOW ???Light travels at a speed

of 300 000 km per second. At this speed, light from sun reaches the Earth within about

8 minutes

Sun light travels a distance of about 150 million km to reach the Earth.

DID YOU KNOW ???You feel the energy in

light when you stand in the sunlight, your body

absorb the energy & you feel it as heat.

If you absorb too much of that

energy, it harms your skin & you get

a sunburn.

Department of Mathematics and Science

Properties of Light & laser.•Light from a bulb doesn’t have as much energy as sunlight.•A light bulb gives off heat because an electric current heats up the filament, or wire, inside the bulb. This makes the filament give off light.•The sun & a light bulb give off light in all directions.•A laser gives off light in a narrow beam.•Inside a laser, light waves line up, like the members of a band marching in step in 1 direction.•When the waves come out of the laser, they stay together & don’t spread out.

Department of Mathematics and Science

Properties of Light & laser.•The concentrated light is very powerful but it can also be dangerous .•Light energy coming out of laser is so concentrated that some factories use laser to cut steel!!•Light coming out of a light bulb spreads out in all directions. The energy you get fro the bulb decreases as you move away.

Department of Mathematics and Science

LIGHT SCATTERS

Light scatters and looses energy the further away from its source.

Department of Mathematics and Science

Properties of Light•When light hits an object, the object affects the path of light. •An object can absorb light, make it bounce back, or let it pass through.•Some of the light energy that hits an object is absorbed, different colors absorb different amounts of light. ex. Dark colored objects absorb the most light.•Objects don’t absorb all the light that hits them. Some of the light bounces back.•Reflection: is the bouncing of light from a surface•Usually light scatters as it is reflected. transparent•Some objects let some light pass through them are known as: translucent

Angles of Reflection

Department of Mathematics and Science

Properties of Light

•The reflected light that reaches your eye from an object enables you to see the object.•A smooth surface reflects light in a predictable way. The light isn’t scattered, instead, it reflects in a pattern that you see as an image in the surface.•Ex. When you see the sky reflected by the smooth window of a building or when you see yourself in a mirror.•Whether the surfaces are smooth or rough, most objects absorb some light & reflect the rest.

Department of Mathematics and Science

Properties of Light •Opaque: materials that don’t allow light to pass through them. Ex. Book, chair, wall, floor.•Translucent : objects that allow only some light pass through them.Ex. Wax paper & bubble wrap. •Transparent: objects or materials that allow all light to pass through them.•Transparent objects don’t scatter light like translucent objects do.

Department of Mathematics and Science

Light Properties

Department of Mathematics and Science

Light Changes Direction

• Light bends or refracts as it passes from one medium (form of matter: solid, liquid or gas) to another.

• Refraction: is the bending of light as it moves from 1 material to another.

Department of Mathematics and Science

Colors-decided by what is absorbed.

If object absorbs then hides color.• All color

absorbed = black

If object reflects color then see.

• All color reflected = white