Pioneers of Electromagnetism
Scientist |
Contribution |
Key Concept |
Hans Christian Oersted |
Discovered that an electric current produces a magnetic field. |
Electromagnetism link |
André-Marie Ampère |
Developed the mathematical relationship between electric current and the magnetic field (Ampère's Law). |
Direction of Current |
Michael Faraday |
Discovered electromagnetic induction (a changing magnetic field produces an electric current). Invented the electric motor/generator principle. |
Electromagnetic Induction |
James Clerk Maxwell |
Mathematically predicting EM waves and confirming light is an EM wave. |
Unified Theory of Electromagnetism |
Heinrich Hertz |
Experimentally confirmed Maxwell's predictions by generating and detecting Radio Waves in his lab. |
Experimental Confirmation of EM Waves |
⚡ Electromagnetic Waves
EM Waves are disturbances that propagate through space and matter, transferring energy. They are produced by the vibration or acceleration of charged particles.
Nature: They are transverse waves (vibrations are perpendicular to the direction of wave travel) and are non-mechanical (don't require a medium, can travel in a vacuum).
Speed: All EM waves travel at the same speed in a vacuum: the Speed of Light (c = approx. 3.0 x 108 m/s.
Electric Field (E) and Magnetic Field (B) are perpendicular to each other and to the direction of wave propagation. |
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Electromagnetic Spectrum
EM Wave |
Practical Uses |
Radio Waves |
Communication (AM/FM), TV, MRI, Radar |
Microwaves |
Cooking, Satellite communication, GPS, Wi-Fi |
Infrared |
Remote controls, Thermal imaging, Night vision, Heaters, Camera Autofocusing |
Visible Light |
Seeing, Photosynthesis, Fiber Optics |
Ultraviolet Rays |
Sterilization, Tanning beds, Checking Bankbook signature, Detecting counterfeit money |
X-Rays |
Medical imaging, Security scans |
Gamma Rays |
Cancer treatment (radiotherapy), Sterilization of equipment, Checking inside of steel oil pipe, Water sterilization |
The Electromagnetic Spectrum
Characteristics of EM Waves
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Law of Reflection
Law of Reflection
1. The incident ray, the reflected ray, and the normal (a line perpendicular to the surface at the point of incidence) all lie in the same plane.
2. The angle of incidence (Angle i) is equal to the angle of reflection (Angle r). |
Images on Plane Mirrors
Location: distance from mirror to image is equal to distance from mirror to object.
Orientation: always upright
Size: same size as the object
Type: always virtual
- Image formed in a plane mirror is Laterally Inverted - left and right are switched.
Multiple Reflections
To calculate the number of images that are formed we place the plane mirrors tilted at an angle to each other, using the formula:
N = (360/angle) - 1
where: N is the number of images formed.
If the mirrors are parallel (facing each other), they form an infinite number of images. |
Curved Mirrors / Spherical Mirrors
Concave / Converging Mirror |
Curves inward (like an inverted C) |
Depends on object position; can be Real/Virtual, Inverted/Upright, Magnified/Reduced |
Convex / Diverging Mirror |
Curves outward (like the letter C)) |
Always Virtual, Upright, and Smaller |
Uses of Concave Mirrors:
Used in Dentistry, Shaving mirrors, headlights, Astronomical telescopes, etc.
Uses of Convex Mirrors:
Side-view & Rear-view mirrors, Security Mirror (in grocery stores etc.), Traffic Mirrors, ATM convex mirror, etc.
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Key Terms (Curved Mirrors)
Center of Curvature (C): center of the sphere from which the mirror section is taken.
Focus or Focal Point (F): point where parallel rays converge (concave) or appear to diverge from (convex).
Principal Axis: the line passing through C and F.
Vertex E (V/E): the center of the mirror.
Focal Length (f): distance from F to the vertex E. |
IMAGE FORMATION IN A CONCAVE MIRROR
IMAGE FORMATION IN A CONVEX MIRROR
Curved Mirrors / Spherical Mirrors
A curved mirror is a reflecting surface in which the reflective surface is a section of sphere. There are two kinds of curved mirrors, the concave and the convex mirrors. A spoon is a kind of a curved mirror with both concave and convex mirror. |
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