Unit 3 Lesson 3 Mirrors and Lenses How do mirrors and lenses work?

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1 Big Idea: Visible light is the small part of the electromagnetic spectrum that is essential for human vision Unit 3 Lesson 3 Mirrors and Lenses How do mirrors and lenses work? Copyright Houghton Mifflin Harcourt Publishing Company

2 How do mirrors form images? Mirror Image Light waves travel from their source in all directions and in a straight line. If a light wave hits an object, it may be reflected, or it may bounce off the object. Most objects have rough surfaces that reflect light in many different directions. A very smooth surface, such as a mirror, reflects light in a uniform way.

3 How do mirrors form images? As light hits a mirror, an imaginary line, called the normal, is perpendicular to the mirror s surface. The angle that hits the surface is equal to the angle at which the light is reflected. Law of Reflection

4 How do mirrors form images? Most mirrors are plane mirrors; they have a flat surface. The reflection in a plane mirror is right side up, but reversed left to right. The reflected image will appear to be the same size as the original object. The reflected image will also appear to be the same distance behind the mirror as the original object is in front of the mirror.

5 How do mirrors form images? When you see reflected light, your brain thinks light has traveled in a straight line from behind the mirror. A virtual image is an image that appears to come from a place that the light does not actually come from.

6 How do mirrors form images? A concave mirror is curved inward like the bowl of a spoon. Concave mirrors cause parallel light waves to converge, or come together. Parallel light rays shining toward a concave mirror converge at a point called the focal point.

7 How do mirrors form images? If a light source were held at the focal point, the mirror would reflect parallel rays of light. Concave mirrors are useful for producing beams of light and magnifying objects. All images are formed where two or more rays from the same location on an object converge. Copyright Houghton Mifflin Harcourt Publishing Company

8 How do mirrors form images? Concave mirrors can form either virtual images or real images. A real image is formed where light from an object converges. A real image can be projected onto a screen. A virtual image cannot.

9 - Reflection and Mirrors Concave mirrors can form either virtual images or real images. The type of image formed depends on the location of the object. When light rays actually meet, a real image forms

10 - Reflection and Mirrors Concave mirrors can form either virtual images or real images. The type of image formed depends on the location of the object. When light rays actually meet, a real image forms

The type of image formed depends on the location of the object.

11 - Reflection and Mirrors Concave mirrors can form either virtual images or real images. The type of image formed depends on the location of the object. When light rays actually meet, a real image forms When light rays don t meet, a virtual image forms

12 How do mirrors form images? A convex mirror curves outward like the back of a spoon. Convex mirrors cause a beam of light to diverge, or spread apart as if it came from a focal point behind the mirror.

Convex mirrors are useful because they make small images of large areas.

13 How do mirrors form images? All images formed by a convex mirror are virtual, right side up, and small. Convex mirrors are useful because they make small images of large areas. They are used for security in stores and factories. Many cars, buses, and trucks use convex side mirrors so the driver can see more of the surrounding area.

14 How do lenses form images? A lens is a clear optical tool that refracts light. Under a Lens Refraction occurs when a light wave changes speed as it passes from one medium to another. The change in speed makes the light waves bend and either converge or diverge, depending on the lens.

15 How do lenses form images? Light from an object passes through a lens to form a real or virtual image. The type of image depends on the shape of the lens and how close the object is to the lens.

16 How do lenses form images? A converging, or convex, lens is thicker at the center than at the edges. It is often convex on both sides. Parallel rays of light converge at a focal point after they pass through a convex lens. The distance between the lens and focal point is called the focal length.

17 How do lenses form images? Convex lenses are used to magnify or focus light. They are used in magnifying glasses, telescopes, microscopes, binoculars, cameras, and projectors. Convex lenses are used in eyeglasses to correct for farsightedness.

18 How do lenses form images? A diverging, or concave, lens is thinner at the center than at the edges. Light that passes through a concave lens is refracted outward as if from the focal point. Because they are refracted away from each other, parallel light waves passing through a concave lens do not meet.

19 How do lenses form images? In concave lenses, the distance between the object and the lens does not make a difference in the type of image that is formed. Diverging lenses are used to spread light, often in combination with other lenses in telescopes and binoculars, and to correct for nearsightedness.

20 Virtual or Real Orientation Size of Image Optical device Real-world example Virtual Right side up Larger Real Upside-down smaller Virtual Right side up smaller Virtual Right side up larger Real Upside-down smaller Virtual Right side up smaller Convex lens Concave Mirror Concave Lens Concave Mirror Convex lens Convex Mirror Magnifying glass headlight Eyeglasses (Nearsigted) Makeup mirror Camera Your eye Security mirror

21 MIRRORS Concave Curves inward Convex Curves outward Rays always meet - converge Real images Enlarged images Virtual images Reduced images Upright image Rays never meet - diverge Upside-down image

22 LENSES Convex Thicker in the middle Concave Thinner in the middle Rays always meet Converging Real images Enlarged images Virtual images Reduced images Right side up Rays never meet Diverging Upside-down

23 Big Idea: Visible light is the small part of the electromagnetic spectrum that is essential for human vision Unit 3 Lesson 3 Mirrors and Lenses How do mirrors and lenses work? Copyright Houghton Mifflin Harcourt Publishing Company

24 P Use words or phrases Concave MIRRORS Convex

25 P Use words or phrases Concave LENSES Convex

Thin Lenses Drawing Ray Diagrams

Thin Lenses Drawing Ray Diagrams Drawing Ray Diagrams Fig. 1a Fig. 1b In this activity we explore how light refracts as it passes through a thin lens. Eyeglasses have been in use since the 13 th century. In 1610 Galileo used two lenses