Transcript File
Light and Sound In this unit: 1) 2) 3) 4) 5) 6) Properties of light Reflection Colours Refraction Properties of sound Hearing What is light? Light is a kind of energy. Without light energy you could not see anything!!!!!!!! Light energy gives things colors, helps plants to grow, can power solar batteries to make electricity and is used in lasers. Part 1 – Properties of Light Light travels in straight lines: How does the following experiment prove this?????? Laser Shadows Shadows are places where the straight lines of light are “blocked”: Rays of light Light travels VERY FAST – around 300,000 kilometers per second. At this speed it can go around the world 8 times in one second. Light travels much faster than sound. For example: 1) 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 blast first and then hear the bang. Luminous and non-luminous objects A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objects Reflectors Dispersion of light Dispersion of light is separating of light into its different colours Colour White light is not a single colour; it is made up of a mixture of the seven colours 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. Prisms bend or refract light! The colors of the rainbow: Red Orange Yellow Green Blue Indigo Violet Seeing color The color an object appears depends on the colors of light it reflects. For example, a red book only reflects red light: White light Only red light is reflected We see things because they reflect light into our eyes: Homework Properties of Light summary 1) Light travels in straight lines 2) Light travels much faster than sound 3) We only see things because they reflect light into our eyes 4) Shadows are formed when light is blocked by an object 5) Light is a form of energy like heat and electricity Part 2 - Reflection Reflection from a mirror: What do you notice about where the mirror puts the light you shine into it? Normal Reflected ray Incident ray Angle of incidence Angle of reflection Mirror Using mirrors Mirrors reflect all the light! Two examples: 2) A car headlight 1) A periscope Refraction Refraction of light is the bending of light as it passes from one medium to another Refraction through a lens Convex Lenses cause light to converge or come together because one or both sides curve outward. Looking through a convex lens make things look: ???? Refraction through a lens Concave Lenses cause light to converge or come together. Looking through a convex lens make things look: Applications of Refraction Telescopes contain lenses which refract light they allow distant objects be seen Microscopes contain lenses which refract light, they allow small objects be seen Prisms refract light and are used in cameras and binoculars Contact lenses and spectacles refract light and correct defective vision Sound – The basics We hear things when they vibrate. If something vibrates with a high frequency (vibrates very ______) we say it has a _____ pitch. If something vibrates with a low frequency (vibrates ______) we say it has a ____ pitch. The lowest frequency I could hear was… Words – slowly, low, high, quickly Drawing sounds… This sound wave has a _____ frequency: This sound wave has a ___ _frequency: Drawing sounds… This sound wave has a _____ amplitude (loud): This sound wave has a _____ amplitude (quiet): Hearing problems Our hearing range can be damaged by several things: 1) Too much ear wax! 2) Damage to the auditory nerve 3) Illness or infections 4) Old age (not like Mrs. Powers) Other sound effects… Like light, sound can be… 1) Reflected – sound reflections are called ______. 2) Refracted – this is why you might sound strange if you try talking underwater The Ear Label your diagram with the following: These bones are vibrated by the eardrum This tube carries the sound towards the eardrum This part is used to help us keep our balance This part “picks up” the vibrations This part of the ear contains many small hairs with turn vibrations into an electrical signal This part connects the ear to the mouth This part “channels” the sound towards the ear drum The Ear