E09 Waves, Electromagnetic Spectrum & Optics

Mechanical Waves A disturbance that transfers energy from place to place Medium- material that a wave travels through.Ex- air, water, earth. Mechanical waves need a medium. NO MEDIUM, NO WAVE! CAUSE?-energy causes the medium to vibrate back and forth & up. and down. Types of Waves Classified how they move through a medium

Transverse Move at right angles to the direction to the direction that they move. Crest- highest part Trough-lowest part.

Longitudinal Move the particles of a medium parallel to the direction that they are moving. Compression- where the energy is close together. Rarefactions- parts where the energy are more spread apart.

- What Are Waves? Longitudinal Waves The compressions of a longitudinal wave correspond to the crest of a transverse wave. The troughs correspond to rarefactions.

Surface Waves Combinations of both waves Happens on the surface of two mediums.

Properties of Waves Frequency- Number of complete waves that pass through a given point in a certain time. Period motion- any motion that repeats at regular time interval. Period- the time required for one complete motion to return to its stating point. Hz- Hertz is one vibration per second

Properties of Waves Wavelength- λ - The distance between two corresponding parts of a wave Crest to crest, trough to trough, etc…

Properties of Waves Speed-How far a wave travel in a unit of time. Speed= Wavelength x Frequency Frequency= Speed / Wavelength Wavelength= Speed / Frequency S FW

Properties of Waves Amplitude-Maximum distance the particles move in relation to the resting point. The more energy the Higher the amplitude

Interactions of Waves Reflection-wave hits an object that it can not pass and it bounces back. What you see depends on how light bounces off an object.

Interactions of Waves Refraction- When a wave enters a new medium at an angle, one side of the wave changes speed before the other side, causing the wave to bend.

Interactions of Waves Diffraction-When a wave moves around a barrier or through an opening in a barrier, it bends and spreads out.

Interference When 2 or more waves meet. Destructive- when 2 waves combine to form a wave with a smaller amplitude. Constructive-when 2 waves combine to form a wave with a larger amplitude.

- Interactions of Waves Standing Waves If the incoming wave and a reflected wave have just the right frequency, they produce a combined wave that appears to be standing still. Video-

Electromagnetic wave are transverse waves that consists of vibrating electric and magnetic fields that move through space at the speed of light. EL/ Mag waves can travel through a vacuum, and do not need a medium to travel through- Radiation

Waves or Particles? Light has many properties of waves. But light can also act though it is a stream of particles. Photon= An individual particle of light energy. (packet) Photoelectric effect- When a beam of light is shined on an object and causes electrons to move causing an electrical current

Radio Waves Longest wavelength and lowest frequencies. Radios- Am/Fm,TV, Microwaves, radar, wifi. MRI, ultrasound & cell phones

Infrared Energy given off as heat Night vision

Visible Light Longest to shortest wavelength: red, orange, yellow, green, blue, & violet Human eye can only see wavelengths from about 400nm-to -700nm Mixture of colors

Ultraviolet (UV) Higher frequency and shorter wavelenght than visible light Can damage of kill cells Used to kill bacteria and viruses. Skin uses it to produce vitamin D UVA rays cause skin aging and wrinkling and contribute to skin cancer, such as melanoma

UVB rays are also dangerous, causing sunburns, cataracts (clouding of the eye lens), and effects on the immune system. They also contribute to skin cancer. Melanoma, the most dangerous form of skin cancer, is thought to be associated with severe UVB sunburns that occur before the age of 20. UVC rays are the most dangerous, but fortunately, these rays are blocked by the ozone layer and don't reach the earth.

X-rays Can penetrate most matter Used to take images of bone inside the body. Bones absorb the x- rays and do not let them pass.

Gamma Rays Shortest wavelength and highest frequency Most penetrating of all From radioactive elements Used to kill cancer cells

When Light Strikes an Object… Types of surfaces: 1.Opaque: material that reflects or absorbs light. Can not see through. Metal, wood,ect 2.Transparent: light passes through. ( transmits). Glass, water, air. 3.Translucent: some light can pass through. Frosted glass, wax paper

Mirrors Sheet of glass with a silver-colored coating on one side. Image- is a copy of an object formed by reflected or refracted rays of light. Plane Mirror- Flat - produces an image that is right-side up and the same size as the object being reflected.

Concave Mirror A mirror with a surface that curves inward like the inside of a bowl is a concave mirror. Focal Point is the place that the rays of light meet.

Concave mirrors Concave mirrors can form either virtual images or real images. Virtual Image-are right side up or upright. It is a basically a copy. What you can see but, does not exist. Real Image-light rays meet at a point. They are upside down, or inverted. They can be smaller or larger than the object.

Convex mirror A mirror with a surface that curves outward is called a convex mirror.

Refraction The index of refraction of a medium is a measure of how much light bends as it travels from air into the medium. The table shows the index of refraction of some common mediums

Lenses A lens is a curved piece of glass or other transparent material An object’s position relative to the focal point determines whether a convex lens forms a real image or a virtual image.

Concave Lenses- curve inwards towards the center and are thicker on the ends. A concave lens can produce only virtual images because parallel light rays passing through the lens never meet.

Convex Lenses- thicker in the middle and thinner on the ends

Concave lenses are used to correct nearsightedness. Convex lenses are used to correct farsightedness