Light and Sound

Part 1 – Properties of Light Light travels in straight lines: Laser

Light travels VERY FAST – around 300,000 kilometres per second. At this speed it can go around the world 8 times in one second.

Albert Einstein

Light travels much faster than sound. For example: Thunder and lightning start at the same time, but we will see the lightning first. 2) When a starting pistol is fired we see the smoke first and then hear the bang.

We see things because they reflect light into our eyes: Homework

Shadows Shadows are places where light is “blocked”: Rays of light

Properties of Light summary Light travels in straight lines Light travels much faster than sound We see things because they reflect light into our eyes Shadows are formed when light is blocked by an object COPY

Part 2 - Reflection Reflection from a mirror: Mirror Normal Incident ray Reflected ray Angle of incidence Angle of reflection Mirror

LIGHT & ITS USES - Reflection I. Reflection – Bouncing back of light waves A. Regular reflection – mirrors smooth surfaces scatter light very little. Images are clear and exact. B. Diffuse reflection – reflected light is scattered due to an irregular surface. COPY

Regular vs. Diffuse Reflection Smooth, shiny surfaces have a clear, regular reflection: Rough surfaces have a diffuse reflection. Diffuse reflection is when light is scattered in different directions COPY

FOCAL POINT Focal Point – Point where reflected or refracted rays meet and image is formed COPY

Lens Lenses have two sides, and either side can be plane, concave, or convex A lens is a transparent object with at least one curved side that causes light to bend (or refract). COPY

Concave Lenses - All images are straight and appear smaller. - Lenses that are thicker at the edges and thinner in the center. Diverges (spreads apart) light rays The De-Magnifier COPY TOP ONLY

Convex Lenses Thicker in the center than edges. The Magnifier Lens that converges (brings together) light rays. Forms real images and virtual images depending on position of the object The Magnifier Convex Lenses - THE MAGNIFIER

What if the mirror isn’t flat? Curved mirrors What if the mirror isn’t flat? 2) A car headlight 1) A periscope

View kacleaveland's map "Have you ever approached a giant concave mirror? See your upside-down image suspended in mid-air. Walk through the image to see a new reflection, right-side-up and greatly magnified. In the background you see reflected a room full of visitors enjoying other Taken in a place with no name (See more photos or videos here) View kacleaveland's map Concave Mirrors Curves inward May be real or virtual image COPY

Convex Mirrors Curves outward Reduces images Virtual images Use: Rear view mirrors, store security… COPY CAUTION! Objects are closer than they appear!

Part 3: Refraction of Light Refraction – Bending of light waves due to a change in speed through an object. Prisms – Glass that bends light. Different frequencies are bent in different amounts and light is broken out into different colors. COPY (IN COLOR)

Refraction (Cont.)

Words – speed up, water, air, bent, medium Refraction Refraction is when waves ________ or slow down due to travelling in a different _________. A medium is something that waves will travel through. When a pen is placed in water it looks like this: In this case the light rays are slowed down by the water and are _____, causing the pen to look odd. The two mediums in this example are ______ and _______. Words – speed up, water, air, bent, medium COPY (Exit Ticket)

How You See Near Sighted – Eyeball is too long and image focuses in front of the retina Far Sighted – Eyeball is too short so image is focused behind the retina. © 2000 Microsoft Clip Gallery © 2000 Microsoft Clip Gallery

LIGHT & USES: Lenses Concave Lenses – Vision – Eye is a convex lens. Nearsightedness – Concave lenses expand focal lengths Farsightedness – Convex lenses shortens the focal length.

Color White light is not a single color; it is made up of a mixture of the seven colors of the rainbow. We can demonstrate this by splitting white light with a prism: This is how rainbows are formed: sunlight is “split up” by raindrops.

Color of Light Transparent Objects: Light transmitted because of no scattering Color transmitted is color you see. All other colors are absorbed. Translucent: Light is scattered and transmitted some. Opaque: Light is either reflected or absorbed. Color of opaque objects is color it reflects. © 2000 Microsoft Clip Gallery

Color of Light Color of Objects White light is the presence of ALL the colors of the visible spectrum. Black objects absorb ALL the colors and no light is reflected back. FINAL SLIDE – Color of Light © 2000 Microsoft Clip Gallery

The End