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Mirrors and Lenses

Date post: 15-Apr-2016
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Mirrors and Lenses And how brain adapts to the image reflected or absorbed
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Page 1: Mirrors and Lenses

Mirrors and LensesAnd how brain adapts to the image reflected or absorbed

Page 2: Mirrors and Lenses

Goals• At the end of the presentation the student will be able to

correctly differentiate between absorption, reflection and refraction.

• At the end of the presentation, the ss will be able to correctly differentiate between the three types of mirrors.

• At the end of the presentation the ss will be able to differentiate between the three type of lenses.

• At the end of the presentation the ss will correctly understand how mirages are formed.

Page 3: Mirrors and Lenses

Concept Words• Focal point• Absorption• Reflection• Refraction• Convex• Concave• Convergent• Diffuse• Mirage• Mirror• Lens• Prism

Page 4: Mirrors and Lenses

Light• What is light?• Light arrives on our planet after a speedy trip from the Sun,

149 million km (93 million miles away). Light travels at 186,000 miles (300,000 km) per second, so the light you're seeing now was still tucked away in the Sun about eight minutes ago. Put it another way, light takes roughly twice as long to get from the Sun to Earth as it does to make a cup of coffee!

• During the 20th century, physicists came to believe that light could be both a particle and a wave at the same time. (This idea sounds quite simple, but goes by the rather complex name of wave-particle duality.)

• It is made inside of atoms when they get “excited” . It makes the atom unstable and its liberated in the form of a photon.

Page 5: Mirrors and Lenses

Reflection , Refraction and Absorption

In order to understand this topic we will refer to the following url: http://studyjams.scholastic.com/studyjams/jams/science/energy-light-sound/light-absorb-reflect-refract.htm

Page 6: Mirrors and Lenses

Mirrors• It is basically anything with a smooth surface that reflects

almost all of the light that hits it. The key factor is a smooth surface, because rough surfaces scatter light instead of reflecting it.

• The mirror image is reversed, which you can easily see if you stand in front of a mirror with a shirt with words on it. The words on the shirt appear backwards in the mirror.

• The first mirrors were likely polished stones, such as obsidian, then they were changed to brass, and then to clear glass coated with a thin layer of reflective metal.

• The mirrors in most places are plane mirrors. They are flat and reflect the objects in front of them accurately, maintaining the same relative size and position of the objects reflected.

Page 7: Mirrors and Lenses

Mirrors (cont.)

• What happens when you look in a mirror? In the daytime, light reflects off your body in all directions. That's why you can see yourself and other people can see you. Your skin and the clothes you're wearing reflect light in a diffuse way: light rays bounce off randomly, haphazardly, in no particular direction. Stand in front of a mirror and some of this light from your body will stream in straight lines toward it.

• How does the mirror reflect light? The silver atoms behind the glass absorb the photons of incoming light energy and become excited. But that makes them unstable, so they try to become stable again by getting rid of the extra energy—and they do that by giving off some more photons.

Page 8: Mirrors and Lenses

Types of mirrors• If the surface of a mirror is perfectly flat (what's known as a

plane mirror), what you see in the glass is a reasonable approximation to what's really there—but with one crucial difference: the image appears to be shifted from left to right (we say it's mirrored, but scientists say it's "laterally inverted").

Page 9: Mirrors and Lenses

Types of mirrors (cont)• If the mirror bows inward at the center (known as a

converging mirror or concave mirror), light rays will appear to come from in front of the mirror, the reflection will be nearer to you, and reflections will appear bigger than they really are. That's why a converging mirror magnifies. Shaving mirrors work like this.

Page 10: Mirrors and Lenses

Types of mirrors (cont)• In a mirror that bulges outward at the center (a diverging

mirror or convex mirror), the opposite happens. Light rays seem to come from behind the mirror and reflections will appear smaller and further away than they would in a plane mirror. Driving mirrors work like this (and so does the back of a spoon if you hold it just right).

Page 11: Mirrors and Lenses

Diagrams of mirrors

Page 12: Mirrors and Lenses

What happens with the image?• Diagram

Page 13: Mirrors and Lenses

Lenses• A lens is a transparent piece of glass or plastic with at least

one curved surface, that works by refraction. That means the rays seem to come from a point that's closer or further away from where they actually originate—and that's what makes objects seen through a lens seem either bigger or smaller than they really are.

Page 14: Mirrors and Lenses

Types of lenses• CONVEX LENSThis type of lens is thicker in the center than at the edge. Parallel rays of light entering it on one side will converge (meet) at a particular spot on the other side of the lens. Magnifying glasses and microscopes use convex lenses. The image will appear bigger than the real one.

Page 15: Mirrors and Lenses

Types of lenses (cont.)• Concave lensesA concave lens is thinner at the center than at the edge. Parallel light rays passing into one side of the lens diverge (spread out) as they emerge from the other side. If you are nearsighted, your eye lens focuses a scene just in front of the retina in your eye and the image you see is blurred. A concave lens spreads out the light rays before they enter the eye, so that they are focused on the retina and the image is sharp.

Page 16: Mirrors and Lenses

What happens with the image?

Page 17: Mirrors and Lenses

What happens with the image?• Diagram:

Page 18: Mirrors and Lenses

Is a mirage a real image? * Mirages happen when the ground is very hot and the air is cool. The hot ground warms a layer of air just above the ground.* When the light moves through the cold air and into the layer of hot air it is refracted (bent).* A layer of very warm air near the ground refracts the light from the sky nearly into a U-shaped bend. Our brain thinks the light has travelled in a straight line.* Our brain doesn't see the image as bent light from the sky. Instead, our brain thinks the light must have come from something on the ground. URL: https://www.youtube.com/watch?v=S9CztTYuGqg

Page 19: Mirrors and Lenses

Movement of light through a medium • Depending on the type of matter it comes into contact with, light will behave

differently. Sometimes light will pass directly through the matter, like with air or water. This type of matter is called transparent. Other objects completely reflect light, like an animal or a book. These objects are called opaque. A third type of object does some of both and tends to scatter the light. These objects are called translucent objects.

• Light moves at the fastest known speed in the universe. In a vacuum, light travels 186,282 miles per second! When light travels through matter, like air or water, it slows down a little bit.

• Normally, light travels in a straight path called a ray, however, when passing through transparent materials, like water or glass, light bends or turns. This is because different materials or mediums have different qualities. In each type of medium, whether it is air or water or glass, the wavelength of the light will change, but not the frequency. As a result, the direction and speed of the traveling light wave will change and the light will appear to bend or change directions. Example: Light refracted in a prism gives away different colors.


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