# James Clerk Maxwell (1831 – 1879)

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James Clerk Maxwell (1831 – 1879)

Electromagnetic (light) Waves
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AM vs FM radio Frequency Modulated Amplitude Modulated

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.

Microwaves 7

Infrared 8

Thermogram We radiate infrared light aka “heat” 9

Visible 10

Ultraviolet 11

X-RAYS 12

Gamma Ray 13

Reflection and Refraction of Light
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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. 15

Law of Reflection θi θr 16

2 types of reflection: 17

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With diffuse reflection, your eye sees reflected light at all angles
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. 20

θi>θr θi<θr θi θi θr θr 21

The Index of Refraction
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Snell’s Law of Refraction
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A ray of light is incident on the surface of a block of clear ice (1
A ray of light is incident on the surface of a block of clear ice (1.309) at an angle of 40.0° with the normal. Part of the light is reflected and part is refracted. Find the angle between the reflected and refracted light. 24

Frequency Between Media
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b) its frequency in zircon c) its wavelength in zircon.
The light emitted by a helium–neon laser has a wavelength of 632.8nm in air. As the light travels from air into zircon (1.923), find a) its speed in zircon b) its frequency in zircon c) its wavelength in zircon. 26

Illusions from refraction
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Sunset not really there?
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Mirage 30

Dispersion 31

Variation of Index of Refraction with Wavelength
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Critical Angle 33

Total Internal Reflection
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TIR and ‘bling bling’

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 36

The Rainbow 37

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 38

A bright underwater flood light at the bottom of a 2
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. 39

MIRRORS

Image Types for Mirrors
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Image characteristics:
TYPE – B) ORIENTATION C) MAGNIFICATION (M) D) Position & height of image and object 42

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.

Properties of the Image Formed by a Plane/Flat Mirror
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Concave Mirror Converges light rays after reflection 45

Parallel light rays reflecting off of concave mirror
Note how all 4 rays reflect and converge at common point. This is called FOCAL POINT. 46

Focal Length Incoming rays are parallel and all reflect through a common point called the FOCAL POINT, F. 47

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 48

Convex Mirror Diverges light rays after reflection 49

APPLICATIONS: 50

RAY DIAGRAMS

Characteristics of image:
Object inside the focal point. Characteristics of image:

IMAGE IN CONVEX MIRROR

Mirror equation 54

Magnification

Example A concave makeup mirror is designed so that a person 25cm in front of it sees an upright image magnified by a factor of two. What is the radius of curvature of the mirror? 56

Example2 How far from a concave mirror with a focal length of 22.5 cm must an object be placed to produce an image with a magnification of +3.65? 57

Thin Lenses Use same formulas as mirrors, except that f ≠ R/2…doesn’t apply 58

Converging or Convex Lenses
The difference between mirrors and lenses is that mirrors reflect and lenses refract light. 59

Parallel rays refract through converging lens and then proceed through F on other side.

Diverging or Concave Lenses (THICKER AT EDGES)
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Parallel rays refract through diverging lens and then diverge where rays can be traced backwards through F on incident side.

Ray Diagram

Diverging lens

Sign convention for lenses
Where you expect light to end up is assumed positive (opposite side of lens) Converging lenses have +f Diverging lenses have -f

Example Based on the picture shown, describe the type of lens and the type of image If the magnifying glass was immersed in water, what effect (if any) would that have on parallel rays leaving the lens? 66

APPLICATIONS OF LENSES
Overhead projector (lens + mirror), eyeglasses, contacts, magnifying glass, telescopes, microscopes, your eye, etc 67

The ability of the eye to instantly adjust its focal length is known as accommodation.
Your ciliary muscles flex and manipulate the curvature and shape of your lens which changes the focal length of the lens. 69

Farsighted 70

Nearsighted 71

Astigmatism means that the cornea is oval like a football instead of spherical like a basketball. This causes light to focus on more than one point in the eye, resulting in blurred vision at a distance or near. 72

Combinations of Lenses

Combination of Thin Lenses
The image produced by the first lens is calculated as though the second lens were not present The light then approaches the second lens as if it had come from the image of the first lens The image of the first lens is treated as the object of the second lens The image formed by the second lens is the final image of the system 74

Example An object is located 4.75m from a simple optical system consisting of two converging lenses. The first lens of this system has a focal length of 100 mm and the second lens, which is 20.0 cm from the first lens, has a focal length of mm. What is the magnification of the system? 75

Example 2 An object is placed 20.0 cm to the left of a converging lens of focal length 25.0 cm. A diverging lens of focal length 10.0 cm is 25.0 cm to the right of the converging lens. Find the position and magnification of the final image. 76