AM vs FM radio Frequency Modulated Amplitude Modulated
Both AM & FM radio signals have advantages and disadvantages. • Generally, AM waves have much longer wavelengths than FM waves and can DIFFRACT better than FM waves and can travel greater distances before the signal fades. FM is more direct line of sight. • However, because information is coded in the amplitude of an AM wave, power lines and lightning can influence the amplitude and are more likely to interfere with the AM wave. • FM has a greater range of frequency which is better for music whereas AM is better for talk radio since there isn’t much fluctuation in a person’s voice.
Thermogram We radiate infrared light aka “heat”
Reflection and Refraction of Light
Rays instead of waves approximation A ray of light is an imaginary line drawn along the direction of travel of the light beams. We use this instead of a wave.
Law of Reflection θi θr
With diffuse reflection, your eye sees reflected light at all angles. With specular reflection (from a mirror), your eye must be in the correct position.
Refraction of Light When a ray of light enters a different medium at an angle other than 0o with the normal, it will bend or REFRACT due to a speed change due to material change.
θi>θr θi<θr θi θi θr θr
A ray of light is incident on the surface of a block of clearice (1.309) at an angle of 40.0° with the normal. Part of the lightis reflected and part is refracted. Find the angle betweenthe reflected and refracted light.
The light emitted by a helium–neon laser has a wavelengthof 632.8nm in air. As the light travels from air intozircon (1.923), find a) its speed in zircon b) its frequency inzircon c) its wavelength in zircon.
Fiber Optics and TIR Plastic or glass rods are used to “pipe” light from one place to another This ‘light’ can be used to carry information at light speed Fiber Optics, Medical Endoscopes
Observing the Rainbow If a raindrop high in the sky is observed, the red ray is seen A drop lower in the sky would direct violet light to the observer The other colors of the spectra lie in between the red and the violet
A bright underwater flood light at the bottom of a 2.75-m deep pool is positioned 1.85 m from one edge of the pool. At what angle will light emerge from the surface of the water at the edge of the pool. Assume the pool is filled to the brim with water.
Image characteristics: • TYPE – • B) ORIENTATION • C) MAGNIFICATION (M) • D) Position & height of image and object
Reflection & Image Formation by a Plane Mirror What you see when you look into a plane (flat) mirror is an image, which appears to be behind the mirror.
Concave Mirror Converges light rays after reflection
Parallel light rays reflecting off of concave mirror Note how all 4 rays reflect and converge at common point. This is called FOCAL POINT.
Focal Length Incoming rays are parallel and all reflect through a common point called the FOCAL POINT, F.
Applications of concave mirror PARABOLIC REFLECTORS - Behind flashlight bulbs, headlights, searchlights. projects light out in a concentrated beam…bulb is placed at focal pt. SATELLITE DISH - Microwaves strike dish and reflect and collect at the receiver (at focal point) SOLAR COOKER MAKEUP MIRROR…provides an enlarged image of face when held close to face
Convex Mirror Diverges light rays after reflection